Today I tried my first backflip on a trampoline and landed on my neck with my knee landing squarely in the middle of my forehead. I think it's just a commitment problem, like you said, but it's so subconscious that I can't stop myself from freezing up upside-down. I need to practice being upsode-down for a while, I think...
ouch lol. dont worry, i've seen a lot of people land like that on their first try.
if you get a spotter and just have them spot you a couple times you'll be able to do them on a trampoline no problem.