Same feeling I've been having.
Crankley
Dealing with this as well. Pretty crippling when I find myself without an engaging hobby. It got really bad during the COVID years.
Finding the slow plod out of the depths has be helped by creative activities. I have about 5 projects on the go currently. As ambitious as making a video game to as unimportant as making a small felted sheep.
I didn't get my diagnosis till I was in my 40s but I found the professional acknowledgement to be helpful. I find it a lot easier to forgive myself for the wasted time and unfinished projects. I've also found the ability to forgive myself makes returning to dormant projects a lot easier.
I recently moved to the back and beyond (not helpful at all) but it highlighted how important it is to have people that move you away from your patterned behaviors. Face to face time with another person with ADHD and the same interests is a gold mine for helping break routine getting you to engage and making you feel positive about who and what you are.
Don't get down on yourself for not being able to find the answers right away. Look for the small things that make life easier and the moments that tend to sap you of energy and limit those (I wear only white tshirts and jeans, have 30 odd pairs of the exact same socks to avoid decision fatigue around getting dressed).
Not sure if it's helpful but I'm a post 40 child and I'm still finding new things to do. I don't do as well with learning as I used to but I can attest to the fact that you can still get good at lots of stuff. I've learned things like knitting, mountain bikeing, programming, stone masonry, car repair all fairly competently all in my late 30s early 40s.
For me the no.1 take away is self forgiveness. When you can stop wasting energy on the fact that you didn't accomplish what you wanted, realize that we are biologically hardwired to feel that way and instead give yourself a high five for trying, it definitely gets easier.
Best of luck, hope you get a chance at some point to
Tangential... Do you ever think it's kind of bizzare that we have instances of a fictional character having infamous lines or quotes but in actuality a different human wrote it who and will often not recieve any credit. Not at all a criticism, just an odd thought. Sorry for the diversion.