Hi Monokuma,
I can completely relate to what you are saying here. 10 years ago I had a picture of what my life would look like at 29. It was something to look forward to and I just thought it was the natural progression of things. I didn't know that my mom would die when I was 21, or my dad would remarry years later and kick myself and my brothers out of the house we grew up in, I didn't know I would go through 3 different jobs and still not be able to find one that lets me afford my rent or that I would be diagnosed with MDD and that my dad would tell his entire family who now all think I'm crazy. I recently got back in touch from a friend from a couple years ago, who I wanted to catch up with, and now every time I think about all the things that have happened since her and I lost touch, it's never anything good. And I don't think she wants to hear that so that's probably not going to happen.
My life at 29 is eat, sleep, work. And that's all I have to look forward to, which isn't much.
You don't have to have a "horrible" life to be depressed about it. You don't have to have a reason to be depressed. You can feel however You feel and just know those feelings are valid, regardless of what your life looks like in comparison to someone else's.