1.Fig. to grieve; to be sorrowful. (Fixed order.) She has been eating her heart out over that jerk ever since he ran away with Sally.Don't eat your heart out. You really didn't like him that much, did you?
2.Fig. to suffer from envy or jealousy. (Usually a command.) Yeah, the reward money is all mine. Eat your heart out!Eat your heart out! I won it fair and square.
you should be sorry for the choices you have made I thought I'd become famous, and I could say "Eat your heart out" to every girl I'd ever gone out with.
Usage notes: usually said as if it were an order, as in the example