【喻】事情乾開了頭，就不能不乾到底（一般指不好的事或有風險的事）。而家經已洗濕個頭咯，點收倒手啊？（現在已經乾開了，怎麼罷得了手？）

describes a situation where a person has already started in doing something and it is not a good idea to turn back or stop half way; literally 'the head is already wet'; to be entangled in a situation that can not be withdrawn easily