I went through a phase like that at one point in my life. But it was only because I was concentrating on myself. I did find it a little difficult to start actually contributing to the friendships I had but it's never a bad idea to start by buying rounds at the bar, or letting loose at concerts/sporting events. Actually work on making your friends feel better about themselves by complimenting them on their attire or their opinions on stuff. Be positive in general. Avoid bringing up negative things. People gravitate to people who make them feel good about themselves.