So, this is a step aside from the few preceding posts, and is not in reference to them. Just want to be clear about that before addressing something that's tricksy to put into words, and -- well, I hope it's not as depressing as it may initially seem. That isn't the intention here.
Whenever I start to think about these issues, and I think about them more often than I'd like, there's a quote that comes to mind.
It isn't a happy quote. It is still one of the truest things I have ever seen put into words.
It's this:

There are a few quotes, poems, songs, bits of art and similar that I come back to pondering often, for one reason or another. This is one of them. It's what I'd call a 'frequent companion' when these specific feelings emerge.
For a long time, I looked at it as commiseration. It was, at least, a reminder that I am not alone in having these feelings.
My thoughts and feelings about it have evolved considerably since, without losing the bits that were useful before.
The second realization it helped me internalize was that: this is natural, normal, and human. We don't have to have a mental disorder or illness to experience this. It's part of life for all of us. Nobody has a perfect record of victory in this regard, no matter who they are. That does not make any of us lesser in some way, and it's important to remember that. We talk a lot in this hobby about the opportunities provided by failure in the course of a story, or for a character, and we liken it to life as a nod to 'realism'. And then we promptly forget that when it comes to our own failures much of the time, because those monsters and ghosts are very, very loud, and they speak our language like little else ever will.
So we're up to: you're not alone in this, and this is part of being human; it does not make you broken, sub-par, or lesser. It's the third one that's big, and it's the third one that's -- cliche as it may sound -- the charm.
Sometimes they win.
It isn't going to be every time. Not unless you give up trying. It is so important to remember that.