When I was 13, I couldn't wait to grow up--as did most people. I hated being restricted to PG-13 movies and rated R movies weren't even an option. Now that I'm not 13 anymore, It's crazy to think that my parents aren't going to be there for every little bump in the road and that I have to figure your problems out for myself.
Every kid dreams of the day they can start driving. You think that having your license is the be all and end all of adulthood--you can drive yourself anywhere you want. But that feeling is only temporary. You'll start to miss the times your dad used to drop you off at your friend’s house and when your mom brought you to all of your lacrosse games.
You have to start paying your own bills, especially if you live in an apartment. The pay check you wait for every other week ends up being used on rent, grocery shopping, etc. Life becomes about budgeting and being smart about saving and spending. When you were in middle school, it was as easy as asking your parents for money every now and then to use when you went out with friends. The financial burden is larger than you think it is.
You will become distant with a lot of your friends. As each of you start living your separate lives, it'll be harder to plan dates to hangout. You can't talk about that history teacher you used to hate anymore. The options you have for topic of conversation can't help but decrease and you guys will start to have less and less in common. Chances are, you won't end up ever speaking to your best friend from 6th grade again.
Every decision you make impacts not only you but everyone else around you. This is true to any situation, but it becomes more apparent as time goes on. When you're contemplating whether to take your dream job offer, you have to think about your family, location, friends and most importantly yourself. If you have roommates, you have to consider every little thing like deciding when to shower so you don't bother them. Growing up means establishing yourself in society and you can't do that unless you're aware of how you are making your decisions. It's almost terrifying to have to make your own decisions with little to no guidance.
Lastly, the world isn't as pure and nice as you once thought it was. The more people you interact with as you grow up, you'll see that there are those that want to tear you down and hate watching your success. It won't be like kindergarten where everyone tells you that your finger painting is the most beautiful thing in the world. This isn't to say that there aren't going to be positive influences around you, but it is something that I wish I knew earlier.
It's great that you're finally becoming your own person, but there are times that you'll miss the innocence and care free attitude of being a child. Life only gets more complicated as time goes on. So take this into consideration: no matter what stage you are in life, take a step back, slow down and enjoy the moment.