I got like this early on. I’m experiencing it now with my ADHD: not diagnosed til I was 28 (34 now) and only just starting to understand how it affected/affects EVERY part of my life - particularly social matters. Can’t help but be sad sometimes that I struggled so much for so long without knowing why I didn’t seem to understand the world and people the way others did.
Anyhow. It’s definitely normal and healthy to mourn the time lost to drink/drugs, but just be careful to not get hung up on it. We can’t change the past, we can only work for a better today.