If you could do better, you would be.
You are just going off what you know.
You are constantly growing and learning how to "do human" better (even if you don't realize it or it seems really slow).
"Not good enough" is a sign you want to try and do a good job.
Your failures are merely opportunities for growth. Without them, you wouldn't know how to succeed.
Even self-destruction is your subconscious attempt to get a release (and make yourself feel better; a little sign that you still value yourself).
Give yourself a break.
Forgive yourself for your inevitable human imperfections (we all have them).