You find out a lot about yourself when training for a marathon, and on the day when you are running it. It is in many ways an analogy of life; 'life is a marathon not a sprint'. Will you give up when it gets tough? Will you fight for it and make it through the tough times? Nothing worth having comes easy and if you want it, you have to work damn hard for it and earn it - there are no free rides in the marathon (or life).
"In anything in life; sport, love, family, friendship, you get out exactly what you put into it... It is always better to have put too much into something, to have given your all, despite running the risk of burn out or over exposure, than be the person who is afraid to put their complete effort in for fear of failure or not wanting to stray out of their comfort zone."