burn one's bridges
burn one's bridges also burn one's boats {v. phr.}
To make a decision that you cannot change; remove or destroy all the ways you can get back out of a place you have got into on purpose; leave yourself no way to escape a position.
Bob was a good wrestler but a poor boxer. He burned his boats by letting Mickey choose how they would fight.
When Dorothy became a nun, she burned her bridges behind her.
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Source: A Dictionary of American Idioms