IDIOMS

eat one's Wheaties

(US and Canada, idiomatic) To prepare or fortify oneself for an activity requiring exertion.

Example: 1971 Oct. 19, Haney Reilly, "Another game, another loss but Hawkeyes looked better," Telegraph-Herald (Iowa, USA), p. 17 (retrieved 1 July 2011):
  But he just couldn't get the ball through the goal posts (poor Harry . . . he didn't eat his Wheaties, or else his shoe was on backwards).
1994 Sep. 11, "Garbage Collector Lifts Away Worries," Miami Herald, p. 1B:
  Jo-Ann Wonsik answered a Herald want ad for a career requiring day after day of heavy lifting. . . . "And you've got to eat your Wheaties on this job," she said.
2008 Dec. 10, Felicity Barringer, "Science Students Get a Real-Life Lesson, in Science Fiction," New York Times (retrieved 1 July 2011):
  Of all the movie promotions in all the towns in all the world, Keanu Reeves had to walk into this one: a California Institute of Technology forum at which he was asked, “How could an alien being grow so fast without violating standard mass- and energy-conservation laws?” . . . He paused. “I ate my Wheaties.”