I think that building and maintaining friendships might be founded on a general interest and curiosity of one person towards another.
Maybe I'm always too concerned with myself to be able to think of the other person. But if I manage, on occasion, to pry my thoughts away from me, what should I find interesting about the other person?
Do I look for similarities and/or differences in personality and interests? Do I look for characteristics that I admire in the other person? And there must be some kind of interpersonal magic that people use to suss out these characteristics in others. I mean, they can have what appears to me to be a boring casual conversation, yet they appear to have gotten some deeper meaning out of it. And when I try to achieve meaningful conversation, people look at me like I'm speaking a different language.
So what draws you into another person's life? What interests you about a stranger, enough that you would seek social engagement with that person. How does one make social interactions meaningful and supportive, or at least, make them seem less of a burden?
What you say about being too concerned with yourself strikes a chord with me at this point in my life. I have far less faith in how I'll be from one day to the next to be able to invest much time in another person. It takes all my energy just to deal with myself, which I find very annoying. Fortunately I have my ex-wife and my son.
I used to have a lot of friends when I was younger - I'm not a hard person to get along with, or I wasn't before. I think it's as
said - people can sense if you're caring and decent and they'll want to be around you. It's pretty hard to fake caring about someone - or liking them. Just as I think it's probably impossible for anyone else to say what you should be looking for in another person. That's an extremely personal thing - I've been close to people that were very different to me, but there was just something about each other that we liked.