Most of the time, it's worth focusing on the long-term--protecting the kid's capacity for intrinsic motivation, as my current favorite writer on teaching and parenting would put it. But when the three year old is kicking the infant in the head, I care less about what Gareth will be like when he's forty and more about Conrad's still-open fontanelle.
So last time Gareth demanded that I sing my much-Bowdlerized version of Please Stop Kicking My Head by kicking Conrad's head, I took swift action.
With a foam rubber scimitar--purple, two feet long, and glow-in-the-dark.
Brandishing the scimitar aloft, I shouted, "Avast, matey, stop yer head-kickin' or walk the plank!"
And the head-kicking stopped.
"But Pirate Captain Mommy," Dan pointed out, "walking the plank might be kind of fun."
"Har, it be too late for plank-walkin'. It be nearly bedtime, and the mosquitos be out. Tooth brushin' instead, Cap'n's orders!"
Immediate compliance, about tooth brushing, with a smile.
On occasions when we have an epic parenting fail, we imagine the kids will need years of therapy to recover from us, but at least their therapists will be entertained.