As your moving your fingers over your engorged cock, try to completely relax your pelvis area. Focus on how your fingers feel gliding over the head, then the entire shaft and back to the head again. Short, long, short long...
Imagine that you are paralyzed from the waist down...but can still feel the pressure building in your loins. You want to seize your cock and stroke it madly until you explode all over yourself. Instead, you delay your desire.