> but no matter how much I try I never seem to be able to cultivate any kind of lasting relationship with others.
I used to run a startup focused on this, here is what I learned:
Time. The answer is time. Research shows there are two ways long term bonds are formed, shared adversity[1], or lots of time spent together. General rule of thumb for relationship building:
1. 10 hours together is someone you know
2. 100 hours together is a good acquittance.
3. 1000 hours together is a good friend and a relationship that can now last a long time
This is why activities such as football watching (3*18, 54 hours a year, 2 years and you now have the beginnings of a good friends circle), or weekly poker matches (2 hours, almost 100 hours in a year) are so effective at building relationships.
Interpersonal hobbies with lots of down time, like rock climbing or playing in a band, accelerate this process greatly.
For people with kids, weekly play dates, or a weekly rotated dinner hosting.
Friendship is literally grinding hours, when we are young it is easy, studying and hanging out get those hours in, but when we get older, we have to be purposeful about it.
[1] Military boot camps are an example of this, so are the various culture wars. If you make people feel they are part of an oppressed group, preferably while isolating them from society at large, you will forms a cohesive group that acts together and one where everyone feels connected to each other. "Both sides" of the political spectrum do this, once you learn to spot it you start seeing it everywhere.