For me, "that feeling" comes from 2 or 3 things.
1) When I'm sitting in a lawn chair right after a groovy ride, and my legs feel like they are so big they're gonna pop

2) The look a person in a car gives me I pass them going up a hill

3) Standing in line at a store with my helmet tucked underneath my armpit, my shirt is soaked with sweat,my shorts are soaked with sweat,my bike leaning against me, and I down a Powerade in one long pull.

ha ha, good times guys!!!