Keep moving your hand up and down your shaft. Try to go from top to bottom and back up again in one continuous motion.
We've documented that you are excited by the idea of being observed while you masturbate...and that you enjoy being instructed on how to masturbate. We've also established that you like the idea of being denied orgasm. Even when your body is preparing itself to release your cum and it feels like it can't be held back, your mind is able to override this desire with it's own need to prolong the sensation. Would you agree with this analysis?