In addition to not blaming yourself when a girl doesn't accept your advances, you have to stop blaming others for "cockblocking" you.
Nothing bothers me more than when a guy says he didn't get the girl because his friends started talking to him or some strangers started talking to the girl he was interested in or that her friend pulled her away from him.
Not being able to take responsibility for your own short comings is probably why the girl, and people in general, are fine with not spending time with you. When you stop blaming others for your not getting laid, perhaps you will be able to find ways to get laid despite the obstacles you may have to face.
Everyone has obstacles, but there are those who get over them and there are those who blame them. A blamer doesn't get over his obstacles. He wallows in self-pity and bitterness. And I can't think of a lot of people who enjoy being around bitter people.