Probably the hardest thing about being stuck in a black hole is how hard it is to get out, and how easy it is to slip back in without warning. When we feel like that, we lose the ability to believe we can accomplish anything. It ends up being a self-fulfilling prophesy: our mental energy is so sapped by the depression and low self-esteem that we might not be putting forth our greatest abilities. Then we fail and take it as confirmation that we can't win. I was trapped there for most of my life and have only recently gotten out of it and found my path forward. Self-compassion exercises have done wonders for me; I was attacking myself so fiercely that I was pushing myself over that event horizon without even realizing it. I'll post a link to information and exercises to try:
Self-Compassion

It's natural to think in a problem-solving way when we're stuck; we have problems, so we want to fix them. But sometimes we have to work on our emotional and psychological state first, so our thought process will be uncluttered. It's like having an outdated refrigerator sucking up all our brain's "electricity," and expecting ourselves to operate efficiently. "Brain electricity" is a finite resource.


I also don't think it's helpful to look for where blame should fall. (But I do think you're being much too hard on yourself.) I think it's most helpful to find ways to heal, and then once you feel ready you can move forward in a new direction. You have a whole community here eager to support you in your journey,hartbroken.