(idiomatic) To seek to have two things which are mutuallyincompatible (such as eating a piece of cake and yet still possessing that piece for future use).
It's not possible to get your savings and keep the piggy bank intact. You can't have your cake and eat it too!
Usage notes
This expression is usually found in some form of the proverb: You cannot have your cake and eat it too.
Translations
to seek to have two things which are mutually incompatible
Mandarin: 魚與熊掌不可兼得/鱼与熊掌不可兼得(zh)(yú yǔ xióngzhǎng bùkě jiān dé), 鱼与熊掌不可兼得(zh)(yú yǔ xióng zhǎng bù kě jiān dé)("One cannot get fish and bear's paw at the same time."), 又要馬兒跑,又要馬兒不吃草/又要马儿跑,又要马儿不吃草, 又要马儿跑,又要马儿不吃草(yòu yào mǎr pǎo, yòu yào mǎr bù chī cǎo)(You want a horse to run, but won't let it graze.)