一失足成千古恨

a single slip may cause lasting sorrow.

yī shī zú chéng qiān gǔ hèn ㄧ ㄕㄧ ㄗㄨˊ ㄔㄥˊ ㄑㄧㄢ ㄍㄨˇ ㄏㄣˋ