English: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idea to turn back or stop half way; literally 'the head is already wet'; to be entangled in a situation that can not be withdrawn easily
English:an instruction to someone not to overreach themselves, not to take on more than they can cope with, "don't bite off more than you can chew!"; literally: without a big head, don't wear such a big hat