懸崖勒馬(현애늑마)

험한 낭떠러지에 이르러서야 말고삐를 잡아채다.
위험에 직면하고서야 잘못을 깨닫고 돌아서다.

high and steep cliff, and take the reins and stop the horse
rein in the horse at the edge of the precipice

strangled the horse on the edge of the high cliff

pull back before it is too late

desist from doing something before it is too late

act in the nick of time
wake up to danger at the last moment

soberly turn back in time