Cách sử dụng
The expression "save, keep, etc. something for a rainy day" means to save or keep something for when it might be needed in the future. It comes from the idea that if you save something for a rainy day, you will have it to use when you really need it, like when things are difficult or uncertain. It can be used in many different situations, such as saving money for a future expense or keeping extra food or supplies for an emergency situation. It's a good idea to save things for a rainy day so you're prepared for whatever comes your way.