Play what you know and you'll start to feel good about yourself and your confidence will grow.
Writing down goals is always good in any aspect of life - you won't forget where you're heading and why you're going there.
Play every day - even 10 minutes before going to school/work. It'll soon become a habit.
I stopped playing seriously about 20 years ago, only having a little pluck once in a blue moon. Last year I decided I wanted to start performing again and I had my first gig just before Christmas 2012. Anything's possible if you focus on a goal!
And yes, Rock On Man!