Dream Interpretation: What does it mean if I dream about falling?

Ever since I was a kid I've had dreams about falling.

In them, I'd be doing something that involved moving—like driving a race car on one of those tracks with jumps in it, or riding an ATV on a track with jumps. And in those dreams, I'd always go over a huge jump, and I'd begin falling. I'd fall faster and faster until I was just about to hit the ground—then I'd wake up.

I'd like to know what those dreams mean—if anything.