I didn't undertand one sentense. Please help me!
"OK, thanks, I'll take it! I am a bit afraid of falling off. I did that more than once when I was a kid. It doesn't hurt, really, BUT IT SURE KNOCKS THE WIND OUT OF YOU."

I didn't get the part written in CAPITAL LETTERS.

Question

I didn't undertand one sentense. Please help me!
"OK, thanks, I'll take it! I am a bit afraid of falling off. I did that more than once when I was a kid. It doesn't hurt, really, BUT IT SURE KNOCKS THE WIND OUT OF YOU."

I didn't get the part written in CAPITAL LETTERS.

Answer

knock the wind out of someone's sails =
- to bring someone to an abrupt halt by a heavy blow to the body
- to humiliate someone.

Reference: http://idioms.thefreedictionary.com/knock+the+wind+out+of+sails

Answer

When you take a bad fall, particularly on your back, you sometimes can't catch your breath for a few seconds and you have to gasp for breath. We call that getting the wind knocked out of you.