I think my personal biggest mistake was joining the army. I'd go back and never walk into the recruiter's office in 11th grade.
My mentality was so consumed with leaving my town, getting away from everyone that I simply ignored everyone. I wanted to go off and make friends with all my platoonmates in OSUT and then make friends wherever I was stationed.
Lo and behold, I get to the last month of training and I have preexisting medical issues flare up. I get discharged, end up back in Massachusetts with zero contacts and nowhere to go. The funniest part is that I fucking despised about 37 of the 40 other guys in my platoon. I got in physical altercations with a couple of them.
I skipped prom. It messed up my potential with girls. I ignored the entire "senior" experience of high school because I was so "Hooah" I wouldn't risk my military future by drinking or smoking pot.
It's not like I didn't have my fair share of FA potential beforehand. I went to 3 schools (two private ones and then public) in 4 years of HS. That makes it hard to make friends, but it's not like I didn't know the public school kids. I could've done better, I could've played football and baseball and made friends and maybe girls would've liked me - I was actually REALLY good at both sports as a kid.
TLDR: idiot that was too eager to grow up and run away ends up stuck where he started.
Join clubs. Play sports. Be outgoing. Find a niche. There is one somewhere for you.