By realizing how unhappy you are when you're not by yourself.

Most of my life I was really unhappy and it was always because of forced socialization with people I didn't like and who didn't like me. My first job out of college when I no longer had to socialize with people... all the sudden all my depression and negative feelings disappeared. Being alone and only interacting with people when/where I wanted... was super liberating.

And it's only gotten better with time. I do get along with people... but not very many because the people I like generally leave me alone and leave others alone. It's people's incessant need to make other people conform to their expectations that drives me insane. I grew up in a family/town that loved conformity and hated anything/anyone different. College was better, but still a lot of conformity pushers, but grad school and my career are great because the people there were not preoccupied in judging other people for being different than them and actually valued it. I'm finally at the point in my life where I will never have a friend or a partner who ever again who tries to force me to like what they like or behave the way they want me to behave.

And when I think about my friends that have lasted... that is the common thread. They never asked anything from me, they just take me as I am and I take them as they are and we like that about each other.