You can do it (maybe)

From the time that we were all children, we've heard it repeated again and again.  'You can do anything you want'.  This was probably good advice when we were all children.  There was potential and opportunity for many of us (but for some still none, we just blatantly lie to them) and we weren't jaded by the world.  We all had goals about the great things that we were going to do.  Some were doctors, astronauts, governors, presidents, or even humanitarian aid workers.

But as time goes on I understand more and more that the things that I dreamed of having when I 'grew up' will never happen.

Guess what part of the equation you're missing?

Sure hard work will pay off in some way, but it won't give you back your 20/20 vision, so you can kiss your F-14 Tomcat goodbye (They retired it anyway).  Your hours of study will sure help with your grades, but do they have cardiology classes on how to steady that shaky hand of yours (You really wanted to be a pediatrician anyway, children are more rewarding.)?  And of course the most relevant information for all of us is  this:  You're not that smart.  Your hours of study can't change the simple genetics that will forever separate you from Stephen Hawking (But at least you can play hop-scotch, right?).  

Yet another thing he has that you don't.

So as your childhood dreams are shattered and you sell out, because you've also realized money does buy some happiness, think of the achievements in your life.  And try not to let it get you down.