When you're in high school, you daydream about how life is going to be when you are in your 20s. You imagine that you will be out of college, at your dream job, and on the town every night while being a social butterfly. You think that you won't have any problems because you will be independent, young, and most importantly: free. I hate to be a Debbie Downer, but keep dreaming. As it is the same with everything in life, the grass always looks greener on the other side.
I won't lie, it is pretty awesome making your own rules and doing what you want- but that can set you up for big failure down the road. You never realized how much you needed your parent's guidance until you are struggling to get your ass out of bed for class in the mornings after a late night. Lets not even get into the shock that paying bills can be. I'm not saying it's awful being at this age in my life, but it's not quite the dream I once imagined it would be.
Bills
Like I said, bills can be a real pain in the ass. If you didn't get much experience paying your own bills growing up, it's a huge wake-up call. Back in my high school days, all of my hard earned money went for gas and cheap beer. Now, my bills take up the majority of my check, and the rest goes to my family. My priorities are very different now than they were then, so I almost don't even mind them anymore. I do strongly believe that schools should drop some of the lessons we will never use again, and teach us important life skills like bills and taxes, so that they are not a huge shock to us when we are booted out on our own.
Work
I have been working my entire life. Ok, I may be exaggerating a little; I have been working since I was 15. It's safe to say that I have plenty of experience and an awesome work ethic. The only difference is, when you are working as a young teenager you are doing it for fun and spending money. As an adult, you are doing it to survive. It's so tempting to say screw it and blow off work to go do something more enjoyable -- but you can't. My advice to you is to do what you love, and turn it into a career. No matter what it is, if you love it and are good at it, you can make a living off of it. Life is too short to follow the crowd and go to law school because your family is pressuring you into a "stable" job.
Health
No matter what your age is, you should make your health a priority. If you don't, it may come back to haunt you down the road. For me, I ate a bunch of crap and didn't take care of myself at all. That lead to even worse habits as an adult, and it made it a hell of a lot harder for me to lose the extra weight and get to a healthy size. Even though I am healthier in my 20s than I was in high school, there are still many health issues we still have as adults. Like acne, for example. My skin may even be worse than it used to be -- which I didn't think was possible! Adult acne is very real, and very annoying. Take care of your skin and try to prevent pimples early on so you are not left with bumps and scars later on.
People
Even if you were the most social person in your class, I guarantee you that at some point that will go away. There will come a time where you will want to do nothing but hole yourself up in your living room in your comfiest yoga pants far away from anyone else. I become more of an introvert the older I get, but I don't mind it. There is nothing better than unwinding and relaxing away from the hustle and bustle of being in public. I think it's a good thing to enjoy your own company, and a little (or a lot, in my case) alone time never hurt anyone!
Your life will change so much, and many different times. The best thing you can do is learn to roll with the punches and take it all in ease. Being young is amazing, and so is growing older. They each have their own ups and downs, so don't take any of it for granted. One day you may look back and miss the way things used to be, before you had bills and responsibilities.