I spent most of my life wanting to become an officer in the army of navy. My grandfather was in the navy during WWII and I was mesmerized by his war stories as a kid. When I grew up a bit I was still attracted to the idea of decision making under pressure and experiences that were meaningful and at the various emotional extremes.
Then in year 10 I discovered two things. Punk rock and biology. I loved biology and at my high school our biology classes had oddly clinical focus. So medicine became the dream. After a while the punk rock lifestyle of sex, drugs and rock 'n roll (READ: No sex, some rock 'n roll and lots of drugs) got to me a bit. Having always been a total nerd, my grades were still good but not high enough for medicine (you do medicine straight out of high school here in Aus and your grades have to be absurdly perfect), so I thought about the combination of extreme experiences, decision making under pressure and medical crap, and a paramedic degree popped into my head.
Being too lazy to write the application essay for paramedics, I started a science degree instead, realized research was not for me, had a brief stint in ICU owing to my drug and alcohol abuse, got clean and motivated, and returned to the paramedic degree the next year.
Four years on I can't think how it could have worked out better.