I started going to new restaurants, exploring new roads or streets, taking wine + paint classes for no reason, googling DIY crafts just to pretend like I'd actually follow through with them, then actually follow through with them. I tried new things, ate new foods, met new people -- even though I was in the same city.
Doing things that genuinely make you happy will actually make you happier. And when you are happier, more people will want to be around you, and make you happy. It's a chain reaction that might sound cliche, but cliche things are just that for a reason.