What happens when you sacrifice everything and get nothing?

I've sacrificed my entire life from a young age for one dream (becoming a doctor). I studied so hard to get into a good college in high school. I'm almost done with college and have spent all my time studying, volunteering, etc. I could say it was all worth it if I achieve my dream. But what if I don't get in? My whole life would have been for nothing. "Kid from white trash family gives it his all and more, and still fails" would be the summary of my life. All those times I could have blown off homework in high school to have fun. All those times I wanted to go out and be a young adult where I stayed at the library. All those times I wanted to date seriously but had no time in my crazy schedule of extra-curriculars to go out on dates. I'm pretty determined so I'd probably keep trying no matter what, but it is just a scary thought to sacrifice so much and possibly get nothing back.