Quote: "Believe you can and your halfway there>"
-Theodore Roosevelt
This is so true circumstances in my life have left me doubting myself every step of the way, there is absolutely no way you can move forward if you don't think you can.
Stop beating yourself up that is the first thing you should do. Remember you may not be responsible for what happened in your past and there is nothing you can do to change your past.
But now you do things to help improve your future, no more negative self talk, you can change things. Start small find at least one thing to be grateful for everyday make this a habit. Next whenever you find yourself coming up with reasons why you can't succeed, STOP and find at least 3 reasons why you can succeed.
You will start to see changes once you start believing in yourself.