A life plan at 19 does seem crazy. In fact its completely ridiculous, your goal in life should be to cram as much fun stuff as possible in before you die, and that is by no means a plan with any direction.
However, I know what I'll be doing.
I'm going to university. I know what I want to take (physics). I want to take it because it interests me. I'm not going to study my ass of 24/7 in university - I'm going because its fun. I intend to ski, party, learn, and have fun. No regrets.
I want a Ph.D. I want to do research in that field. If I'm doing research in the field I'll likely be a prof. Seems like an awesome job to me - sharing something I'm passionate about is something I love doing. If I just get a bachelor's in physics and that's it, such is life. I enjoyed doing it, and it can almost certainly lead to solid careers. No regrets.
I'm going to keep skiing. I'm going to start tramping when the ski season ends around here, and I'm going to go ramping when ramps open. I'm going to try to go to Mt. Hood or something for a few weeks this summer. I will work all spring to raise the money for it. When next season rolls around I'll hopefully be at UBC which means I'll get to ride whistler twice a week, and more on breaks and such. Maybe if I keep working hard I'll win some comps, get noticed. If not, I got good at skiing, I had fun and I'm happy. No regrets.
Music - I play quite a bit of piano. When ski season dies down I'm going to start writing music again, I'm currently saving up for a synth, and maybe I'll be in a band, or maybe I'll eventually put out good enough music to get signed. Music is something I can plausibly keep doing for the next 10 years before I'm past my prime, so this is a realistic option. If it doesn't pay out, then I learned a lot, I had fun, such is life. No regrets.
Basically, do stuff because you want to do it. If you want to ski 8 months a year, you'd better be damn ready to work your ass off for the other 4, but you can certainly do it. Will it lead to a profession? Maybe not, but doing something for a long time will often take you places. Either way, work hard in whatever you do, have as much fun as possible, live with no regrets and do what you want. You'll get places no matter which road you go down, as long as you don't keep turning around.