you can’t have your cake and eat it too

this phrase is easier to understand if it is read as “you can’t eat your cake, and have it too”. obviously once you’ve eaten your cake, you won’t have it any more. used for expressing the impossibility of having something both ways, if those two ways conflict.
he works so hard to pay for that fancy house of his that he never has any time to stay home and enjoy it.

yeah, you can’t have your cake and eat it too.
something that is bittersweet.
getting a good half and a bad half to something.
john: so tom did u get that english cl-ss you wanted?

tom: yea man. i love it. however the teacher is a total b-tch!

john: yea, well you can’t have your cake and eat it too.
an expression basically meaning that you can only have it so good, and you can’t have it all.

an good example is if a situation is bittersweet.
sara was sad that the guy whom had gotten very close to her in the past 3 years which she held a secret fondness for developed an interest in her best friend, clare. in conversation with clare, sara explained the situation, to which clare responded.

“you can’t have your cake and eat it too.”
you cant enjoy what is yours. you can work or you can enjoy.

example:
you work really hard and finish a report, someone else takes credit.

or

you have a gorgeous girlfriend whom only others enjoy in bed.
you enjoy fishing and eating fish, you catch a fish, but your wife eats it.

she says “you can’t have your cake and eat it too”