Grey's Anatomy, Season 8

Meredith:
[voiceover] Our intentions are always pure, we always want to do what's right, but we also have the drive to push boundaries. So we are in danger of taking things too far. We're told to do no harm while we're trained to cut you open with a knife. So we do things when we should have left well enough alone. Because it's hard to admit when there's no problem to treat, to let it alone. Before we make it so much worse. Before we cause such a terrible damage.