you can't sit in two chairs with one butt
proverb You cannot do or accomplish two things simultaneously, so you must be decisive in choosing or pursuing one. Possibly from Yiddish. The Prime Minister will have to make a decision on how to deal with this soon. You can't sit in two chairs with one butt. Look, either be with me here, or go take the job in London. It's your choice, but you can't sit in two chairs with one butt.
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