Why does Tom Brady always choke in the playoffs?

he's a really good qb but always chokes in the playoffs for some reason always plays horrible in the playoffs. 2006 losing that lead to the colts in the afc championship game. 2007 in the superbowl, last year at home against the ravens, and now this year after he beat the jets 45-3 in the regular season, he plays like he did on sunday and cost the pats the game. Why can't he succeed in the playoffs?