I have a 3-year-old with a stubborn streak deep as the Pacific Ocean. (Can any other parents relate?) Here's a scenario that happens often at my house--
Me: Johnny, go get your shoes on, please, because we need to leave.
Johnny: [keeps playing]
Me: Johnny, I said get your shoes on, please.
Johnny: [keeps playing]
Me: JOHNNY! We need to leave! Shoes! Now!
Johnny: [looks up at me briefly, turns around and keeps playing]
At this point, I, as a parent, have many choices. Many parents don't know they have choices, since nothing kicks a person into auto-pilot (i.e. unconscious programming) like the stress of parenting.