you can’t have your cake and eat it too/you can’t eat your cake and have it too: Common Errors in English Usage Entry for Thursday, March 13, 2014

you can’t have your cake and eat it too/you can’t eat your cake and have it too
The most popular form of this saying—“You can’t have your cake and eat it too”— confuses many people because they mistakenly suppose the word “have” means “eat,” as in “Have a piece of cake for dessert.” A more logical version of this saying is “You can’t eat your cake and have it too,” meaning that if you eat your cake you won’t have it any more. The point is that if you eat your cake right now you won’t have it to eat later. “Have” means “possess” in this context, not “eat.”