For the past year or so I've made an effort not to socialize. Sounds weird, but I figured that the only way I could really see just how much I could focus on SETT would be to cut out everything, even things that seemed somewhat important.
If really good friends invited me to something that seemed like it would constitute quality time, as opposed to just not-being-bored-time, I would go as an exception. Through those infrequent occasions, I'd meet new people once in a while. And sometimes these new people were just so amazing that I couldn't help but become friends with them, too.
For the first few years in San Francisco, I felt like I had tons of acquaintances, but only a few really good friends, and even those friends were people I knew before moving here. Even some of the people I hung out with a lot were just acquaintances-- our friendships never deepened, and when they moved away it didn't really feel like a loss.
Now I feel like I have no acquaintances and a lot of really good friends. There are a few people I hang out with who aren't really good friends yet, but it feels like things are moving in that direction.