I've been a teacher for 19 years in Kindergarten, 3rd grade, 4th grade, 5th grade, and 7th grade. My greatest "high" is watching that light come on when a student understands something he/she has been struggling with.
We have a "Trulove Tribe" motto (coined from Harry Wong):
Good, Better, Best,
Never let it rest,
Until the good is better,
And the better is best!