Don't get too frustrated! After a rough run it's a good idea to build up your confidence again on some easier runs (getting back to basics, as other posters said).
Once you're back to feeling like you're king of the mountain, be sure to focus on the bump that comes next, rather than the one right in front of you. It will take time, but your body will eventually learn to absorb rises and falls without your direct focus.
And yes, your board is a tad long, maybe you could sell it to a taller fellow in need! Nitro boards are sick though, be sure to stay with em :P