When I was learning to skateboard I tried going off 5 steps before I knew what I was doing and the board shot out from unde me and I hit right on my tail bone. It was funny b/c I had a similar experience, I thought I was paralyzed, I could not breathe, and I could not move any of my extremities, and I felt like my heart stopped, but I think it was just the fact that I could not breathe. And I almost passed out before I could breathe, I was seeing black spots and crap Anyway it took over a month for it to go back to normal. ... Anyway it is best not to do stuff like that. Where do you board btw? Are you at some ice hell hole? If you are where there is soft snow then 15 feet isn't anything. At targhee people go off a 50 foot drop to a flat landing after it snows b/c it is so soft you can just do a back flop, unless you land in someone elses hole then you get life flighted out...so I suppose it is a bad idea as well.