Whether you only graduated a couple of months ago or it's already been a year or two, you may have noticed the people around you are changing.
Kindergarten through 12th grade was up to your parents.
They're the ones who decided where to live and what school to enroll you in. Basically, everything in your life has been because of the choices they made. However, the same is true for your fellow classmates. You all wound up there because of the life and career path your parents chose, and that might be the only thing you have in common. Of course, it's possible to find some of your best friends this way, but it's okay if some of your best relationships come later in life due to the choices you make for yourself.
While you're still in high school you can begin working, which means an entirely new group of friends/coworkers. Even if you're working in your hometown you all decided to get a job at the same place. Also, coworkers are forced to work with each other, but there's nothing in contracts about seeing each other outside of work. However, one of the best parts of getting a job is all the connections and friendships you make.
Having someone to talk about all the workplace gossip will instantly make your days so much better.
Not to mention you all have at least a vague idea of what each other is earning, so there's no awkward going out to places people can't afford.
Once high school is over your entire social circle is going to change. Even if you listened to others' advice when choosing your school, it was ultimately, for whatever reason, where you belonged.
Maybe it was for completely different reasons, but everyone else there also decided this was the place to be. It might not happen right away, but the people you meet in college are going to lead to very different connections and relationships than people you met beforehand.
Right away you know you have something in common with the people you meet in college.
For starters the people in your classes are (probably) going to have similar interests as you, I mean you did enroll in the same class. Also, if it's a major specific class then I'm positive you already have something in common. Not to mention, that by whatever means (savings, loans, scholarship, or any combination of those) you can all afford the same university.
While it's impossible to predict when or where in life you will meet someone who will change your life, when you get older and start to make decisions on your own, finding these people gets easier. Life is unpredictable and you literally have no control on when people come into your life, but if high school didn't give you the forever friends you were hoping for, there's still a lot of time.