keep your powder dry
保留力量或资源，以备不时之需
口语·劝人保持准备
英文释义
to be prepared and ready for a future opportunity or event; to exercise caution and restraint in order to protect oneself
例句
We don't know when the job market will improve, so keep your powder dry and save your money.
典故来源
源自17世纪的火药时代，士兵需保持火药干燥以确保枪支可用，引申为随时做好准备。