There was a guy
Yellowstar on another dating forum (theattractionforums, i used to visit there, then I came here). I had similar problems (my own beta-ness and mistakes leading to the collapse of whatever I had going with a girl), and his words really helped me. I've transcribed them below:
"""
First of all, realise that you WILL make mistakes. Period. And I will, and every other living human on the planet.
And then, simply forgive yourself. Look at yourself in the mirror and say "yep, I screwed up and that's totally fine and I forgive myself. The only way I can fail is by quitting, but I didn't and kept on going, and actually got valuable experience on what I should and shouldnt do to be better in the future, and therefore it was a success!"
You cant learn to ride a bike without ever falling.
You cant learn math without making a single mistake.
And you cant learn how to have great relationships without ever doing something really stupid
So get up, be a man and keep on going!
Never quit, and you will never lose.
"""