Overall it's made life much more manageable, so I don't feel like I'm constantly juggling too much and dropping the ball and running out of time and letting myself and others' down.
I no longer have a hundred radio stations competing for attention in my brain (just three or four on a bad day), I ruminate less, and I find myself fitting in small tasks in the day that would normally take me months to get round to, if I did them at all. I'm better at finishing things and can spend more than two weeks on a hobby now, without waking up one morning having had any interest in it completely wiped from my memory!
My emotions are much more stable and even throughout the day, which has really helped me feel happier. My anxiety has lessened too, perhaps because things feel more manageable.
I am able to remember to implement coping strategies (like timetabling everything, or buying duplicates of things so I spend less time looking for them) for more than a week, and I'm better at planning ahead now and am rarely late.
I suffer much less often from burnout, and can understand my limits more, to help prevent it - I used to plough ahead trying to do everything and be social all the time (people pleasing is a common feature of adults with late diagnosed ADHD I think, maybe because we're always so afraid of inevitably letting people down/being late/feeling inferior and thus feel undeserving of putting our own needs first) and then after doing so much for a couple of weeks I'd be running on empty and crash, forced to confine myself to my bedroom for a couple of days, unable to do anything, or talk to anyone, feed myself, no concentration, no relaxation, just kind of stuck. I believe I was misdiagnosed with depression in part because of that.
I have much less desire to drink/smoke/overeat etc which were all forms of self-medication, in retrospect. Weed actually effects me like a normal stoned person now, I get a bit silly on it, instead of it just helping me focus enough to read or write in the evening. I now try to exercise instead and take cold showers to boost dopamine if my head is feeling a bit fuzzy.
I still have some bad days (due to hormone fluctuations I believe, from looking at my mood diary) but they're not as bad, because I have experienced many good days and know that it's just one or two days, and even if I do have more bad days, I can seek a change in treatment or try different coping strategies in future.
Hope this all makes sense. If you have any questions about my experience feel free to post them here or DM me x