I crave closeness and friendship but don't try and make friends because I'm a terrible friend and I know it.
Are people telling you that you're a terrible friend, or you just think you are one?
I'm sure my friends will think I'm terrible after they read this.
If you are concerned that you are a terrible friend, then you should think about ways you can improve, because it is good to have and maintain friendships. Consider the things that your friends like, and do nice things for them. Work on communicating and listening to them better.
I can't do that, I only want to be friends with people who are already my friend. It's just better this way.
That's fine, you don't have to always try to gain new friends and just maintain the people that you already are friends with and make sure that you treasure them as your friends. Getting older, it is harder for us to maintain friendships, so I hope you make efforts to stay friends with them and see how you can support one another, not just superficially but also emotionally.