A couple of weeks ago, I took a small stepladder into the back garden and climbed a few rungs to fix a light that had stopped working. It doesn't sound much but I glowed with achievement for the rest of the day. Six months earlier, I would have been too unsteady to risk it, and tilting my head to do the repair would have brought on a surge of vertigo and violent sickness. A year ago, I wouldn't even have attempted it – or cared: I was lying on the sofa, intermittently vomiting and being pumped full of industrial-strength antibiotics to see off a mysterious brain infection that had nearly killed me.

Last May I was struck down by an abscess on the cerebellum, which controls movement, balance and coordination. In the space of a few days, I went from feeling giddy and seeing double, to puking constantly, stumbling and slurring my words. It took four doctors a week to realise I had something worse than an ear infection, by which time I needed emergency surgery, followed by six weeks of intravenous drugs. I barely knew what was going on as I lay in a bed at the Royal London hospital, babbling incoherently. ("Mooing like a cow," my boyfriend Pete cheerfully informed me the other day.) We joke about some of it now, but it was a hellish period with precious few laughs (one of those being when a friend sent a card that read: "Sorry to hear about your man flu").

I returned to work in October and my health continues to improve, but I still struggle with horrible vertigo when I walk and move my head – it's like being on a funfair ride, but minus the fun and you can't step off. The gyroscope in my head is bust. But I'm lucky that my illness left me with just one physical challenge and hasn't affected my cognitive functions. As far as the NHS is concerned, it's effectively case closed. My consultant, John Wadley, whose brilliant neurosurgery team saved me, discharged me last September because scans showed the surgery had been a success. Although no one has ever been able to explain why this particular bacterial infection developed as it did, and why I couldn't fight it off, there's nothing more to be done. The NHS, awesome in a crisis, less so with chronic conditions, must move on to deal with fresh emergencies. A physiotherapist worked with me until January, then left me with exercises and a warning that I would probably continue to get better for a while but then stop short of a full recovery.

I saw a vertigo specialist at Charing Cross hospital privately to learn more. Doctors put electrodes on my head, strapped me into a car seat on a motorised platform, spun me round in the darkness and tracked my eyes with infrared cameras. Then I had to put on blacked-out goggles fitted with cameras so they could watch my eye movements as they alternately pumped hot and cold water into my ears to trigger my balance mechanisms. The experience was comical – it felt like a cruel gameshow – but the result was partially reassuring: everything was working within normal parameters and my lingering symptoms should improve, if not totally pass, in time. Meanwhile an old friend, a specialist physio, is helping with the muscular problems that make my dizziness worse, and I am having acupuncture, which has boosted my mood hugely.

Having a catastrophic illness (the term gives me a slight thrill) is an interesting experience if it doesn't see you off, albeit one you wouldn't wish for. You learn a lot: about yourself, about your friends, family and colleagues, what matters and doesn't. But mainly you learn about the grind of illness and recovery. If you're the sort of person who has only ever had to deal with colds and cuts, food poisoning and the odd virus that sends you to bed for a week of groggy dozing, what strikes you most is the glacial pace of recuperation. You drift through weeks of seemingly changeless days, with only tiny incremental improvements. I had a bad few months with tonsillitis and glandular fever in the 90s, but it was nothing compared with this. A cancer survivor warned me that recovery does not run in a straight line. I now think of it like a stockmarket chart after a crash: the line of health rises from the trough in painfully slow, uneven jags, it plateaus and slips back. Look at the weeks and you despair; only a graph of the year shows a positive picture.

What helps is hearing how other people have managed and triumphed. I see disability all around now, whereas before I think I hardly ever did. I scan people in the street to see how they are coping with obstacles and whether they are masking their difficulties, as I have learned to. Headway, the charity that supports people affected by brain injury, estimates there are around 500,000 people of working age in the UK living with long-term disability as a result of trauma from, say, a fall or a car accident – and that's not counting people who have had meningitis, haemorrhages, tumours or strokes (the last alone affects 450,000 people a year in England). "It's notoriously difficult to get hold of stats for brain injury, for a number of different reasons," says the association's Luke Griggs. "Too many people slip through the net, so often misdiagnosed or completely undiagnosed. One of the frustrating things is we just don't know how many are out there. It would be a scary stat if we could actually get hold of it. And the most frightening thing would be how many people are suffering in silence."

People's stories are different, obviously, but have common themes. Many talk of two years as a benchmark period to regaining something that resembles your previous health. Medics infuriatingly won't ever say how long it will take to recover – perhaps they've never encountered your condition, they don't want to give you false hope or to discourage you, but probably because every case is different. "There's no one route to recovery," says Griggs. "It's incredibly hard to predict what the outcome will be." Left to our own imaginations, we all seem to love creating metaphors and analogies. Griggs recalls a patient who described recovery as "like eating an elephant – incredibly daunting at first, but if you break it down piece by piece, eventually you'll conquer it". Griggs likens it to traffic halted by a motorway pileup: you must take an exit and rejoin at a later junction; some people take a shortcut, but others get lost in the countryside. I have my joyless funfairs, grim stockmarket charts and the image of my illness as cycling at full pelt into a brick wall: my choices were whether, when and how to get back on the bike, which direction to set off in again and at what pace.

David Brown, 35, really did come off his bike. Late one night in April 2008, he was found sitting on the kerb near his London home bleeding from the ear. He's never discovered what happened and there was no CCTV footage. He too was taken to the Royal London Hospital, where doctors found he had a fractured skull and two haemorrhages. Fortunately he didn't need surgery, but the injury removed his sense of smell and left him with tinnitus and various cognitive problems. He has battled through depression and has learned tricks to improve his worsened memory. He used to have a stress-filled job in the entertainment industry. "I was trying to buy a house at the time," he says. "I was still calling the estate agent from my hospital bed, saying, 'Yeah, had a bit of a knock on the head, should be back next week.' Part of that was that I had a brain injury. It wasn't that I was being unrealistic. I wasn't very well." Now, having reconsidered his priorities, he works four days a week for Headway East London.

"I came out of hospital and thought I'd be going back to work within a month. What I found is that it's a really slow process. You see a lot of people with brain injuries returning to work too soon and that's possibly the worst thing they can do because mood is a huge factor in brain injury recovery. If you have your confidence knocked it can really set you back. Since I came to Headway, I have written off any timeline that I was trying to apply. I stopped thinking about how I was going to be for the next six months and started thinking of an investment in me for the rest of my life. It was far better for me to take it easy and slowly introduce new challenges.

"It sounds strange, but I sort of saw it as an opportunity to do something else. I don't want to work full-time again. It's part of the clarity I gained. I was able to slow down for about two years and look around me and take stock of everything." He's just had a baby with his girlfriend. "My lifestyle has improved tenfold. I'm an awful lot happier than I was before. Our relationship has improved. I'm a lot healthier person. I feel I've learned lots of new skills. I'm enjoying a better life in spite of my accident."

Dancing Tango helped aid Sarah Cardwell's recovery from a cyst in her brain. Photograph: Trevor Taylor

When Sarah Cardwell fell ill, she had already made a major lifestyle change. A lecturer at the University of Kent in her early 30s, she had been suffering increasingly bad headaches for several years. Even as her balance failed – she would fall while loading the washing machine – a neurologist agreed with her GP that it was down to stress. So she and her partner, Jon, left their jobs to become dance teachers. A week after setting up Argentine Tango South East, she was diagnosed with a benign cerebellar cyst. She had surgery in October 2007 and tried to start teaching again in December. "I felt that the customers would get tired of me being ill and a hypochondriac, which everyone told me was silly, but once it got to four weeks, I thought, they won't understand what this feels like because they haven't had it. They'll just think I'm malingering. Teaching in the evening meant the days were just knocked out completely."

Ah, the tiredness. That's another thing everyone talks about. It's not a tough-week-at-the-office tiredness that you can rally through with a couple of drinks and the prospect of a weekend lie-in. It's a leaden blanket of exhaustion that sweeps over you – utterly undeniable, non-negotiable and unshakeable. John Horan, a 42-year-old barrister specialising in employment and discrimination, battled it for years after he suffered a brain injury when he was 31: he had a major stroke on the eve of the millennium. He went back to work nine months later, but it was just paperwork while he learned to cope with public transport again. He had his first day back in court after 16 months – two and a half hours arguing a no-hope case for no fee, then a taxi home and straight to sleep for three hours. A decade on, he still has occasional "tiredness issues" yet that's not what he claims has held him back. The Bar Council has a disability equality policy but he thinks it could do better. Although the Bar Standards Board accepts he is "intellectually unimpaired" it questions his oral fluency. He says that while some of his peers have made silk, he can only work in the lower courts and must declare his medical history to clerks, solicitors and judges. The year before he fell ill, he made £102,000; the year after, £5,500. He's doing better now, with fees of up to £80,000 a year, but is furious about how he is treated.

John Horan's brain was injured after a major stroke. Photograph: Graeme Robertson for the Guardian

"The difficulty has not been dealing with my disability at all because I've conquered that, but it's been discrimination because it's all around. It's not that I'm too sick to work. I think the Bar Council has a problem with disabled people. I can't do anything finger-based with my right hand and I walk with a curious gait. That's about it. I can do a better job than most able-bodied people. I'm really good at my job."

The urge to get back to work can get in the way of recovery, but can also be a powerful motivator – it certainly lifted my spirits after four months staring at the living room walls. For Cardwell, it was key. "I realised that tango steps helped me with coordination and not to feel dizzy. We went to a physio appointment shortly after my surgery and she gave me exercises but they were virtually all steps or movements that we get people to practise anyhow. This really made me feel hopeful. It felt like I could recover faster because I already knew how to do those things." She is a little overwhelmed as she recalls dancing with Jon a fortnight after getting out of hospital. "It was me hobbling backwards three steps towards the sofa. It wasn't to music but it was still tango. It counted a lot.

"I remember the recovering in terms of the tango. I remember which steps I could do when. Six months in I could do 'the cross' again. There were certain movements that would trigger a violent pain in my head if I moved my spine in a certain way. It had been achey for a long time, maybe a year or so, and one day I did this movement and it didn't hurt, it was natural."

Relearning apects of your life is a common experience. Cardwell had uncomfortably heightened senses of taste, smell and hearing when she was on steroids after surgery, but lost her sense of self: "I would look through catalogues of clothes and home furnishings, and I had no idea what I liked. I didn't dare express an opinion. It was horrible." Brown also felt disoriented during recovery: "A lot of human activity around me I would watch as if I had just landed from Mars. I felt like I had been rebooted to factory settings."

You make other discoveries too. The heroic partners and families. The people who do thoughtful, kind, unexpected things, who bring lunch, send a homemade pie or arrive in the evening to cook. The steadfast friends who slog through it all with you offering cheery support. And the ones who don't text, phone or visit. Everyone has a small list of those that they puzzle over.

Most of all you learn that you are in a new life, with a beginning that never seems quite complete. TV personality Richard Hammond, who suffered serious head injuries in a 2006 crash, said last year: "From the very outset of the recovery process, I'd get to the end of the week and think, God, I'm better, I'm fixed and then I'd get to the end of the next week and look over the previous one and think, bloody hell, I wasn't but now I am, and that process would go on, and it goes on now." Suddenly a Top Gear presenter sounds like a fount of wisdom to me. What a strange journey this is.

Some names have been changed