have your cake and eat it (too)
US /hæv jʊər keɪk ænd iːt ɪt tuː/
UK /hæv jʊər keɪk ænd iːt ɪt tuː/
1.
to want or try to do two things that are impossible to do at the same time
:
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You can't have your cake and eat it too; you need to choose between your career and your hobby.
•
She wants to work full-time and also travel the world, but she can't have her cake and eat it too.