Back in the day, there was this old powerlifter at the gym I used to work at.  His name was Harry Brown.  Every leg day, I used to see him put himself through absolute torture to find that extra excruciating rep.  Being about 20 at the time, I remember asking him why he trained legs so damn hard...  and he just asks me this:
"You ever seen a big ass tree with a small trunk?"  
I shrugged, said no.  So he says, "if you want to be a big fucking oak, you better have a big trunk."
It's true.  The harder you train stumps, the bigger the rest of you will be.