You didn't know you had ASD (autism spectrum disorder). None of us did, you were just a little odd, outdated, conventional. You learned the rules and followed them well: flowers, compliments, paying for dinners out despite such little cash. You pulled out chairs, held doors and bought thoughtful gifts.

We moved into our first house and it became a little hard. You were far more set in your ways than I expected, inflexible and precise, but being together was new and we both thought it would improve, which over time it sort of did.

Your quiet, self-contained nature drove me quietly nuts. You turned down invitations, left me to go to weddings and parties alone and, most awkwardly of all, were standoffish and abrupt to my friends.

It became easier to do things alone and after realising that, I was relieved but resentful. We bought a house, got married and had a baby. And with that, the rot set in. You were obsessed with your needs, and at times those of the baby, but seemingly never interested in mine. The perceived lack of care for me – as I would lament to friends – continued. Your inability to communicate and have any empathy led me to stop bothering too, and I cannot ever begin to say how lonely that is to live with.

The diagnosis of our child shifted everything as we read up and learned about ASD. The realisation that you were on this spectrum dawned first on me and then on you, with what I don't doubt was great distress to you. For me, there was great sadness, too, as it occurred to me that the things I find hard in you were now never going to change. You were never going to "snap out of it".

As you read this letter, listing my faults – of which there are many – in your head, I should say this: what I have come to see is how hard you have had to work to have the life you have, when for years I assumed the opposite.

The times I was angry that you wouldn't take a risk or push yourself a little more I now see is what you are doing every day.

The things inherent in most of us are a mystery to you, and I realise that you wish they weren't. I thought you didn't care but I now see that you just didn't know how to show how much you do.

I have a respect for you that I never thought I would: for who you are, who you have become and for how hard you have had to work to get there. I know you hate your differences and I know they make you sad but they make you who you are.

I would never say these things. We don't have these conversations. But when you told me, somewhat uncharacteristically, that I have given you a life you never thought you'd be able to have, I realised you might not know that you are precious too.

I know you like a slightly over-the-top sentiment via Facebook. You know I do not. I couldn't bring myself to do that, but I thought this the next best thing and a fitting way to say thank you to you, ASD and all.

Anonymous