Imagine a driver who constantly looks down at the pedals when he's turning at an intersection or who concentrates solely on his hands turning the wheel while he rounds a corner. It's pretty likely that sooner or later that driver is going to wind up crashing into another car, a tree or fire hydrant, or at least running off the road.
That situation really isn't much different than that of a sailor who's in the habit of staring down at his feet or watching his hands flip the sail during a planing step jibe. Sooner or later that sailor is going to crash into another windsurfer, a dock or buoy, or at least wipe out on his own and get wet. Looking ahead at where your board will exit a jibe is as important to sailing your windsurfer as looking ahead while you're turning the corner in your car.
It's a very common problem and one that when eliminated can really pump up your percentage of successful jibes. As you enter the jibe, focus ahead to where you anticipate coming out of it; look around the front of the mast from out over your front shoulder. Not only does this help you gauge the exact area of your exit, but it also helps put your body in a stronger carving position. Looking down as you enter the turn allows the sail to pull your body weight in over the carving rail too much and gives the feeling that you're pushing too hard. The concept is pretty simple; it's getting over the old habit of not looking where you should that takes a little practice. Try it, though; it's sure to help your jibes.