D.K.R.K. - Don't Keep Random Keys. If you keep a key you found, you're

Don't Keep Random Keys. If you keep a key you found, you're just asking for trouble. Don't be a dummy.

I found a key. I kept it. Now I'm stuck with a key that doesn't fit any door. What even is this?

My friend found a key. He kept it. Now he's stuck with a key that leads to a dead end. Total fail.

You found a key. You kept it. Now you're stuck with a key that leads to a room with no light. You're doomed.