Have you ever put yourself through a long-term, difficult process in order to reach an uncertain end?

I’m in my third year (of six) of pharmacy school. At the rate it is going, I know that the next four years are going to be incredibly draining… and then I have a residency on top of that to specialize, so that I don’t end up working retail. I’m great at school (not to sound arrogant) but it is incredibly stressful to me, and sometimes I have a hard time seeing the point in it.. but I (along with most people my age) have been taught that it is the only way I can get to the end career that I want – or at least think that I want. It worries me that I am blindly following a path to an uncertain end. What if I waste six years, to find out that it’s not what I’d hoped for?

So, has anyone else put themselves through some sort of long ordeal (be it college, tech school, monastery, etc) even though you were unsure if it was the right path? How did it turn out?