This little kid and I were talking the other day...

Look at my knees! They're all bruised because I fall a lot!
Ouch, that must hurt.
A little. Do you have any bruises?
Oh yes. I have a really big one somewhere.

He looks down at my knees, but sees nothing. Then he looks at my arms, and sees nothing either.

What? I don't see any. Where is it?
Here.

With my index finger, I point at my heart.

Your heart? How can you have a bruise in your heart? I don't get it.
**You will when you fall in love, kid.