I don't know about other guys, but solitude doesn't do well for me. No real friends, no real family here. Martial arts (for me it's tae kwon do, for you, it can be anything) has filled a big hole in my life.

You get the comradery with adults. The goal setting. The adrenaline of fighting other full grown men. The focus. Etc. In an environment that is USUALLY free of estrogen-laden drama.

I've posted this before, just saying it again, because I really love doing it.

Things like tae kwon do are primarily striking with your feet

Things like boxing are primarily striking with your fists

Things like BJJ are primarily grappling and ground wrestling

Things like Krava Maga are a combination of striking and grappling.

Some like TKD or BJJ are competitive and have tournaments you can go to. There are MANY different combat arts. But if you're looking for something new, or want to check out a new hobby, skip meetups and just go find someplace or someone that will teach you to kick ass :) Lets all the stress out in a positive manner.

Edit:

Be weary of "kick boxing classes" at conventional gyms, sometimes these are estrogen filled hen houses that are more zumba than technique. If you're doing kick boxing, make sure you find one that's not just a cardio class.