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.