I've given a lot of thought recently as to why I am the way I am. Possible reasons I've come up with include:

My life genuinely isn't that good?

I have a partner I love, a nice house and a well paid although boring career, so I don't think it's that.

I have a good life, but not the one I wanted?

I think this is closer. I had dreams of being an artist or musician, or of having a wide circle of friends or an exciting lifestyle. Wild sex. Money was never a goal, oddly. That's one area I've done alright in, but it's not made me happy (although it has helped protect me against other problems) But none of this is me, I'm not that person. I'm not the sort of person who can make these things happen in my life. I feel like my life doesn't have any excitement, but I don't really know how entitled I should feel to that.

Low self esteem?

I don't even know anymore. I used to have low low self esteem when validation from others was important, but it isn't so much now. And sometimes I even think I can be somewhat narcissist, and have noticed traits of the Dunning Kruger effect on my personality, so on that level my self esteem was artificially high. Also as a logical and a slightly socialist person, I don't believe anyone is more important than anyone else, so from that point of view my place in the world is pretty flat. But I do sometimes view myself as something of a loser because of my lack of ability to shake my life the way I want.

I just don't find enthusiasm or happiness in anything?

This definitely feels more like a symptom than a cause. I just really struggle to find happiness in anything. I have hobbies that distract me, and sometimes I even look forward to things, but there's no real enjoyment.

Sometimes I remember a feeling from when I was excited or happy and try to think of ways to get back to that. But then it just makes me sad that I don't feel like that any more. I just don't get the same excitement from simple things like when I was young.

Brain chemistry?

This would be a nice easy answer that can be fixed with pills. I like this answer because it means it's not my fault. but the answer I like is not necessarily the correct one. Medical science does not yet seem to have agreed on whether chemistry can be a cause in itself, and not just a symptom so this can only be concluded as a maybe