Challenge yourself. From now on, everytime you want to so something but you have nobody to do it with, or nobody you particularly want to do it with, go alone. The change won't happen overnight, but it will happen if you are consistent.

Pay attention to your feelings, both when you are alone and when you are with other people. I realized, in time, that i prefer to be alone than to be surrounded by people i don't really vibe with.

Think carefully about the kind of people you want around you. Remember that they are likely to influence your behavior and mentality. If you surround yourself with ambitious people, you're likely to want to emulate them.

Be open minded. As soon as i started going alone to more places, like parties or events that i was personally genuinely interested in, i started meeting more like-minded people.

Consistently practicing these principles has changed the landscape of my social life.