How to be content with yourself?

For a long time I've never been able to accept who I am because I absolutely suck at trying to get a girlfriend. It's depressing me because I realized that's what helps me reach a state of zen; having a significant other. But when I'm alone all I ever do is beat myself down as I envy all the people who are in relationships. Especially my friends who are always getting laid and having girls literally throw themselves at them, while I'm the only one who has to try and most of the times I fail. This feeling of envious emptiness is driving me crazy to the point where I'm getting desperate. I need help! I want to know how to deal with being single and to regain the confidence and esteem that I've lost because of rejection and betrayal. I'm tired of thinking about girls 24/7 and want to go back to being comfortable with who I am. I'm tired of thinking what life would be like if I hadn't made so many mistakes and just want to focus on the future. I'm tired of feeling like a depressed sad little zombie squirrel and want to take the steps to not be afraid to express myself!