Help me get over this self esteem?

I had with a girl about a month ago and since then, I've felt guilty and I realised my mistake and vowed never to do it again. And true to my word, I've not done it again and I seldom talk to her but yesterday i told her never ever ever ever in her life call me or speak to me again or even say hi to me. To be honest, I don't even get the urge to do it again and I have somehow managed to eradicate the temptation. But one problem is still there. I feel kinda LOW about myself and I want to be my old self again, the happy and joy type. Can anyone help me achieve it? Please do not ask me to talk to that girl as she isn't the having remorse type.