I think that everyone goes through ups and downs with the friends they have in their life. I know, for instance, that in graduate school, I had the best friends I've ever had in my entire life, before or since then. I believe that making friends is very much dependent on the situation you're in... work friends don't always translate well into social friends. Social friends are hard to make in a vacuum. A lot of people make friends via school (college, night classes, whatever) or similar interests (hobby classes, yoga, exercise, gym, etc.).

They are all possibilities to try, but I wouldn't pressure yourself too much. Good friends often come naturally into our lives, when we least expect them. Don't be so hard on yourself and be patient... and remember, good friends can also be had online (I've made a few over the years this way).

John