{n. phr.} A very heavy load of worry or responsibility; very tired or worried behavior, as if carrying the world; behavior as if you are very important. * /Don't look as if you had the weight of the world on your shoulders, Henry, just because you have to mow the lawn./ * /John acts as if he were carrying the world on his back because he has a paper route./
See: WEIGHT OF THE WORLD ON ONE'S SHOULDERS.