To have one’s cake and eat it too is a popular English idiomatic proverb or figure of speech, sometimes stated as eat one’s cake and have it too or simply have one’s cake and eat it. This is most often used negatively, to connote the idea of consuming a thing whilst managing to preserve it. This may also indicate having or wanting more than one can handle or deserve, or trying to have two incompatible things. The proverb’s meaning is similar to the phrases, "you can’t have it both ways" and "you can’t have the best of both worlds." Conversely, in the positive sense, it would refer to "having it both ways" or "having the best of both worlds."
This concept, known as opportunity cost, is one of the most important economic concepts.