In college I started praying for God to "cast a searchlight on my heart." I knew I had sin in my heart but didn't know where it was. It was a scary prayer. It continues to be a scary prayer. It's like praying for patience. Note: never pray for patience. It's scary because when God answers it, and He always does, the results aren't pretty. The X-Rays are always pretty nasty.
But it's cool because when He lets me peek at the X-Rays and I am thoroughly grossed out by what I see in my own heart, I get a tiny taste of the grace that's been showered on me. It is only then, when I see how undeserving I am- how sinful I actually am, that I sort of understand grace. It is only then that I weep with thanksgiving for what Christ did for me.
But when I ignore the X-Rays, my teeth look pretty good- especially compared to the rest of the world, especially compared to the British. I fool the world and even myself and it's then that I forget that I am broken. I forget that I need forgiveness and grace. And that is a dangerous thing to forget.