I think the first step towards the life you want is often to just say yes to more things. Accept that coffee invitation from your coworker even if it seems awkward. Sign up for that free class at the library that you're not sure you'll like. Join that club. Book that tour. Say yes to as many things as you can and kill the part of your brain that gut-reacts with a no.
Over the last couple years I adopted an informal policy of "If my reason for saying no is 'eh, that sounds like effort and what if I don't like it' then I should probably say yes."
It's been pretty great, is the outcome. I do weekend tennis with people, and bike riding with them and sometimes brewery visits and poker one time. I did a dodgeball league, and a pickleball league. I was going to a boardgame group for a period of time. I went skiing. I've been to a lot of concerts, and cool restaurants, I've seen old movies that weren't good but now I know about them. And I know so many people because when you go to things you meet friends-of-friends and if you say yes to cool things they're doing then you meet their friends-of-friends. People like it when you say yes to their invitations and come with your best self to see what they've put together.
And I've done a number of things which, in the end, I wasn't actually interested in and did not keep doing. But I can't really think of any things that I regret having tried.
I also want to add that usually I'm the sort of person who needs a 48-hour heads up for any change of plans, and like an additional 72 to process any invitation to something new.
So this is in fact about overriding that reaction. And sometimes overriding it hard.
And it's not a "yes" to everything. It's just trying to live with "yes" as the default answer.
