The correct phrase is "You can't have your cake and eat it too." It means that you cannot have two conflicting things at the same time. The saying implies that you have to make a choice between two options that are mutually exclusive or contradictory.
To "have your cake" means to possess it, while to "eat it too" means to consume it. Once you eat your cake, you no longer have it. So, the saying suggests that you cannot both keep the cake (preserve it) and eat it (consume it) simultaneously.
In a broader sense, the phrase is used to convey the idea that in life, we often face situations where we must choose between different possibilities or desires, and it's not always possible to have everything we want at once. It encourages making thoughtful decisions and recognizing the trade-offs inherent in certain choices.