getting older :|

So, as my 21st birthday nears I have had this overwhelming and very sudden sinking feeling that I am getting old. I know I'm only turning 21 and my life is nearly just beginning  but I feel like I have lived an entire lifetime in the few years I've been living. I started smoking cigarettes, experimenting with drugs, having sex and going to parties when i was 15 years old. Luckily enough I never really got set in those ways and I was through with drugs within a year roughly. I still drink occasionally but I stopped smoking cigarettes after 5 years this past September ( which I am rather proud of). Now that I am going to be of age I will be able to go out to bars and get drinks at restaurants, which is fairly exciting, dont get me wrong, but after this the things I will be looking forward to are getting married, buying my first home, having children, etc.  I will no longer be able to live the life of a bouncy, wild youth! This terrifies me! Everything I do will matter. I will need to find a job that I will want to make a career out of..I will have to save money and most of all I will have to think about how the choices I make will affect my future. It seems like a dream. I feel too young to grow up , if that makes any sense at all. Maybe I am not as mature as I think I am....