Ephesians 2:8-9
I love those two verses. I take it as being the fact that we need Jesus to get to Heaven and that works will simply not get us there because we are inadequate without Christ. But I think it can also be taken as the fact that it is God's grace that saves us and works, good or bad, cannot change that. No matter how bad we screw up, if we go back to Him in humility and honesty, then His grace will accept us back.

Ephesians 2:8-9