Perhaps this will help. There are quite a few things about the body I was born into that are not what I would choose. Contentment is about being happy with what you have got. I would like to be able to sing like Paul Rodgers, but I never will. I can sing like me though.

The unhappiness caused by ADHD and Autisms friction against the modem world has a cure already. Make a more accommodating world. My ADHD/Autism does not make me unhappy. Being in trouble because I work differently to everyone else does make me unhappy though, and that could change. I have lost count of the conversations like 'you are doing brilliant work, 20 years we have been looking for a solution to that, and you stopped up all night one night and fixed it. Amazing, but I can't have you coming in at 9.15, everyone else will think it's ok'. Change that to, 'That's Amazing work, a gamechanger, and since you worked so late, take it easy today, do you need to go home?', and all of a sudden I'm not ill anymore. It is not a disease, just a difference. Do I wish I didn't get upset by things people find normal, yes. Would I have surgery to 'fix' it, no. That is not a path to contentment.