I've read in a book (forgot the name) that sleep paralysis is some sort of defense mechanism during sleep. When you're sleeping the brain is at its most active and when you dream you do all these crazy things. This defense mechanism makes your body's reflexes relax and non-functioning during sleeping, so when you dream that you jumped, it prevents your body from doing it.
Usually in a sleep paralysis you wake up to a stiffened body and your breathing is also affected hence why you feel like you're having difficulty breathing. To break out of a sleep paralysis I usually stretch my feet but I find changing your breathing pattern effective in breaking from a sleep paralysis.