I started at 15, rode for about a year or two, then gave up. I then started again 4months ago (at 20) and in the past 4months ive progressed more than I did in those first 2 years! I dont think age means anything really. Everytime I ride I try to go a little bit bigger, as long as you do this you'll pick it up in no time
I just think to myself whats the worst thats gonna happen, in most cases its a shin dig or sore ass and within 5mins your back up and trying it again, just remember always wear a helmet!
Ive also found that by filming everytime I ride I get a good idea of my improvements, this stops you getting disheartened and keeps you motivated to go bigger and better.