After Helen Rudd sustained traumatic injuries in a traffic accident, she lay in a coma for three weeks. “I had to learn everything again. I had to learn to read and write,” says Rudd. Her life had changed completely and she needed a different outlook. When she heard about an event in which people attempted to live like ancient stoics for a week, the idea struck a chord. In 2014, Rudd was one of almost 2,000 people to take part in Stoic Week. “Stoicism has helped me concentrate on the good things,” she says.

Over two millennia after it first came to prominence, stoicism is having a moment. It’s on the internet, of course: the stoicism subreddit, the largest meeting place for stoics online, has over 28,000 subscribers, many times the number of erstwhile rival Epicureanism (around 4,000). But it is also infiltrating real life, even in its toughest forms. The Navy Seals teach stoic insights to new recruits; throughout the NFL , players and coaches are devouring Ryan Holiday’s guide to stoicism, “The Obstacle Is the Way”. Tim Ferriss, a start-up guru, extols the benefits of Stoicism at firms such as Google. “For entrepreneurs,” says Ferriss, “it’s a godsend.”

Even in antiquity, stoicism was noted for its practicality. Ancient Greek and Roman stoics wrote about theology, logic and metaphysics, but their focus was on the “hic et nunc”, the here and now. “Stoicism tells you what in life is worth having and gives you a way to get there,” says William Irvine, the author of the stoic handbook, “A Guide to the Good Life”. The key is learning to be satisfied with what you’ve got. “Some things are up to us and others are not,” taught Epictetus. “Up to us are opinion, impulse, desire…Not up to us are body, property, reputation, office, in a word, whatever is not our own action.” This indifference to everyday comforts has left stoicism with a reputation for coldness. In reality, its defenders argue, it is simply a rational approach to managing expectations. The central insight of stoicism is that life is tough and changeable, so prepare for difficulty.

Many modern stoics argue that this doctrine has already been partially revived in the form of cognitive behavioural therapy ( CBT ), the “problem-focused” therapy now widely seen as psychology’s best weapon against depression, anxiety and every kind of unhelpful thinking. Like stoicism, CBT encourages practitioners to distinguish between events and perceptions, and nearly every CBT textbook contains some version of Epictetus’s dictum: “Men are disturbed not by things, but the views they take of them.” Yet although the founders of CBT openly acknowledged the influence of stoicism, they tended to adopt the techniques without reference to the wider moral framework. “Stoicism transcends most modern self-help and therapy by offering the view that much of our emotional suffering is caused by false values, such as egotism, materialism or hedonism,” says Donald Robertson, a cognitive-behavioural psychotherapist who is one of the organisers of Stoic Week.

Stoicism is first and foremost a set of beliefs that practitioners can use in a number of ways. “My daily routine consists of a morning meditation during which I contemplate the likely challenges of the day,” explains Massimo Pigliucci. “Then there is an evening meditation, which is the reverse of the morning one.” The Italian-born philosopher came to stoicism when he was going through “something you might call a mid-life crisis”. Since October 2014, he has been practising daily stoic rituals, chronicling his experiences on a blog. “I also practise stoic mindfulness throughout the day,” he tells me, “which basically means to pay attention to the ethical dimension of everything you do.”

The shortage of sources – the major works survive more or less intact, but hundreds of books by lesser-known stoics exist only as fragments – means any attempt to reconstruct stoicism involves a good deal of imaginative interpretation. Even so, it seems a stretch to associate stoic moral self-criticism with the neutral focus of mindfulness. Asking, as Seneca instructs, “What evil of yours have you cured today?” may eventually produce tranquillity, but only after a demanding process of self-examination. The term stoic mindfulness reflects the ambition to philosophise therapy, whereas other writers (most notably Holiday) focus on stoicism primarily as a path to success. Meanwhile, other elements of ancient stoicism – especially the belief in divine providence – vanish entirely from modern accounts. “Stoics held some claims that would be very hard to popularise now,” says Alexander Long, a senior lecturer in Classics at the University of St Andrews. “So the most promising way forward is to offer a selective view of stoicism, one that focuses not on specific doctrines but on the broad framework in which stoics explore ethics and psychology.”

Not everyone is enthusiastic about the prospect of a stoic revival. “Some of the biggest determinants of our wellbeing are socio-economic and political, and I think as stoics we may sometimes forget that,” says the health psychologist Vincent Deary. He tells the story of two cancer specialists who complained to their hospital about working conditions, only to find themselves offered resilience training to cope with the situation. “It’s this idea that we’re not going to change circumstances, so you’re just going to have to get better at dealing with it,” he says. “Are we telling people who we should be helping to get water that they should be resisting their thirst?”

For Helen Rudd, such debates feel like a luxury. “On a personal level, there are some things you can’t change,” she says. These days, she is even able to see the benefits of her accident: she may walk falteringly but, as a result, she looks around. It’s this determination to keep going that binds together stoics ancient and modern. In the words of Seneca: “As long as you live, keep learning how to live.”