1. Just say yes. When someone asks for anything, say yes, no matter how big or small (help them move out, look after their dog) This will put you into novel situations.
2. Show genuine interest in things. Ask why, learn more, dig deeper, keep conversations going by trying to share anything you think is slightly relevant.
3. Dress up. Wear things that stick out, even just a bit, a funky shirt, a nice bright pair of socks, use these to add flare to a standard dark blue and grey world, people will reflect back and be interested in you.
4. Pick one new thing you want to master (not online) my advice here for all round great friend activities - Rockclimbing, Pub Quizes, Boardgame nights, Cycling, Pottery. Each of these almost always need another person to make them work and that helps you grow your confidence.
5. Don't work so hard. Tell your boss you wanna slow it down, try and do 4 day weeks, give back some commitments, take a pay cut. Don't quit just slow it down and give your head some space.
I'm 35, I just quit my /Director of Product role at a successful startup because I wasn't happy. I'm about to go to Thailand to learn how to become a yoga teacher, not for a career but for a disciplined adventure that will deeply enrich me and is nowhere near a computer! You can do it! Put a plan in motion.HN Believes in you! :D