Have your cake and eat it

To want two good things that cannot both be had at the same time.

Examples

You want a big salary and no responsibility? You can't have your cake and eat it.
He wants to travel the world and keep his flat in town – he wants to have his cake and eat it.

How to use it

Informal. Usually negative: you can't have your cake and eat it. American English often adds "too".

the best of both worldsA situation where you get the advantages of two different things at once.