"Every calling is great when greatly pursued." - Oliver Wendel Holmes
It sounds like common sense, but if you take a moment and think about that statement, it is very profound. To pursue something greatly does not necessarily mean that you will succeed, that you will prevail...
It means that you are passionate in your belief that what you are doing is for the betterment of your world, and that it actually IS for the betterment of your world.
Do you have a calling?
Go pursue it greatly.