I wonder about this a lot. I used to be a hopelessly optimistic, positive, happy person despite constant failure. This was of course due to my ADHD, whatever that really is. Over time though, a deep depression, loss of identity, and loss of optimism has really overwhelmed the old me. But where did that begin? Was it there all along? It certainly doesn't seem like it. It isn't rose colored glasses; I had a pretty tough time as a kid. Somehow I was sure everything would be great. Now great things often don't seem as good as they are.
I really struggle to understand where that comes from so I can handle it better. I do believe it developed over time, though. I think it can be reversed. Perhaps that's just a lingering thread of optimism.
I can also relate, but luckily I (hope) that I managed to catch this happening in time and nipped it in the bud. It took a lot of soul searching (plus professional help) to get me back on track.
I started to think that I was a fucking idiot for being incapable of doing what was expected of me, and what I wanted to do. All my grand plans and projects and ideas seemed to just slip through my fingers, despite best efforts I couldn't (and still struggle to) get out of bed in the morning and get to work on time. It was frustrating.
For me it started when I finished university and I realised I had me entire life ahead of me, and no idea what to do with it. As a kid, sure I had plenty of screwups and a tough time, but I always saw the light at the end of the tunnel, I just had to get through my assignments and exams, finish school, finish university, get a job. Once I had done all that I sort of lost all purpose and identity, I had no idea who I was supposed to be. I had grown up with the concept that I was going to get my degree and find a job, then marry some girl, buy a house and have some kids and I'd live happily ever after, like I thought my parents did. Turns out that's not what I wanted in life, and I really struggled to find a purpose.
I think this is incredibly common for all sorts of people with different mental health issues, not just ADHD, I know plenty of people who've experienced the same descent into a hopeless state. Some turn to Jesus, some to drugs, others just say fuck it and kill themselves.
I can relate. I think the daydreams contribute largely to the optimism. When you're young you still have all the opportunity. As you go through life it either does or doesn't match the daydreams. You also get an updated sense of how reality is likely to play out. It can dampen the spirit.
I really struggle to understand where that comes from so I can handle it better. I do believe it developed over time, though. I think it can be reversed. Perhaps that's just a lingering thread of optimism.