You're in a cool age range now where every time you pass a year it's cool. Once you're 16 you feel like a real legitimate teenager, like not a kid anymore but actually a teen. Especially if you get your license. Then when you turn 17 you can see R rated movies and buy M games and stuff. Then obviously 18 is a dope birthday cause you're an adult and can do like whatever you want (excluding drinking and renting cars). I just turned 19 and 19 is cool because like there's this looming realization that soon you'll be in your 20s which makes you feel pretty cool. I haven't experienced 20 and 21, but 20 sounds legit because of the change of decade and obviously at 21 nightlife gets majorly unlocked.
TL;DR: Happy birthday, enjoy the forget out of your next six birthdays.
