Why do I keep hitting myself with a hammer?

From the Episode "The Self Destruct Button"- (The Grey's Anatomy)

   

(At the start)

OK. Anyone who says you can sleep when you die, tell them to come talk to me after a few months as an intern. Of course, it's not just the job that keeps us up all night. I mean, if life's so hard already, why do we bring more trouble down on ourselves? What's up with the need to hit the self-destruct button?

(At the end)

Maybe we like the pain. Maybe we're wired that way. Because without it, I don't know, maybe we just wouldn't feel real. What's that saying? Why do I keep hitting myself with a hammer? Because it feels so good when I stop.