Whenever I come across your posts about that kind of stuff, I keep being reminded of myself some years ago when I was in high school/early college when I was depressed about my situation and myself. I guess I want to mention that there are a lot of people that go through a similar experience, and it's just a growing phase that you'll come out better from. Don't be too hard on yourself if that's part of the problem. You sound like you're ready to learn all that you can from this which seems to be the right track.
For me, I wasn't really happy with who I was at the time. I knew there was some ideal version of me that was better and I just wanted to figure out how to be that person. I thought I needed some honest introspection and self-evaluation to be able to try to change anything about that. I went through a bit of a meditation phase, but I don't think any specific angle of approach is all that important. The most important thing is in the process was that I started to be more accepting of the person I am. I came in with the idea that I could better myself by changing who I was, but instead I just changed my attitude about who I was. I'm still just me. Being able to admit that you have this-or-that flaw, or that you're this way and not that way is where you start to repair your self-confidence and relieve your insecurities. When you start to fix that stuff you realize all the negative things that stemmed from them.