fly off the handle

to become uncontrollably angry; to lose control of one's temper

变得无法控制地生气;失控;控制不住自己的脾气

从字面上看，它指的是斧头在砍树时不小心从木柄(handle)上飞了出来。如果这种情况发生在你身边，你肯定会突然激动，因为它非常可能会误伤到你。

Try not to make Sam mad. He has a tendency to fly off the handle at the slightest provocation.

尽量别惹萨姆生气。他动不动就大发雷霆，一点就着。