I can relate, definitely. I like to be alone but lately I've felt that I'm definitely alone too much. I also have a few very close friends that I see only rarely because we live some distance apart now. I've invited a few people that I work with over to my place, and one couple accepted (we had a great time), but another woman whom I've asked several times, has never been able to make it. That's fine, I understand that sometimes people just don't want to be closer or don't have the time or emotional energy for another friend. But my default is to be alone--I don't feel lonely, though, at least not most of the time. I have a very busy job where I'm in contact with people all day. At day's end, I'm usually drained.
I usually meet people who I'd like to be friends with at work and people who are much younger than me, typically, as many people who are my age seem to have grown old when they are only in their 40s or early 50s. But younger people I think, may not feel I'm in the same place as they are and might not have a lot in common. Perhaps that's just a false perception on my part. I don't push myself on anyone--if I ask a few times and they're busy, I may wait a while before I ask again. I just don't need a lot of friends. I don't like superficial friendships that much. What am I saying?...I do feel if I'm alone too much I forget how to relate very well. I feel my relationship skills get rusty if I'm in my head too much. But then again, it's where I like to be. I need a lot of time to imagine or dream, it's just who I am. Being alone a lot, I find, may make me a better friend because I'm being good to myself and giving myself what I need.