Wow. That looked fun.

I suck at mtb'ing, too.
DH says my issues are all in my head...that I psych myself out of so many things.

Various people have tried giving me pointers, and they boil down to 3 basic things:
1. Speed is your friend. At Kitsune pointed out, momentum carries the day for lots of trail obstacles.
2. Pedal, pedal, pedal. This is closely tied to 1#. Also, "don't give up."
3. Don't look AT the obstacle. Look at the line you want to take. Your bike will go where you are looking. If you look at the rock, that's what you'll hit (ouch!). Incidently, I've found #3 works for downhill skiing, too.