Mogizzle, if that were true, every stoner who ever got the munchies would come down right after eating. Sure, eating something dampens the high slightly, but it won't kill it.

My advice? Do something other than sitting around and worrying about how high you are. Do something to take your mind off it; play some music, eat some food, play a computer game. Most importantly, stand up and walk around. That alone helps a lot.