Why do we FALL in Love ?

I was in a Toastmaster's Club meeting when this seemingly funny question was brought up by one of the guys.

Why do we fall in love , but not rise in Love ?

The creative part of me was up in a jiffy. I said that it was coz I usually go weak in my knees when I see my femme fatale and hence I literally fall in love.

The best answer was giving by a tyro. This is what he had to say :

Before you fall in love, you do your thinking with your brain.
After you fall in love, you do your thinking with your heart.
Your thinking falls from your brain to your heart .... and hence .. .

We fall in love.