To Go Off The Deep End
= to become crazy
*The phrase comes from the idea of learning how to swim. Most smart people would learn in the shallow part of the pool. However, crazy people might want to learn in the deep end of the pool where it is more dangerous.
Ex: Hey I know you like her, but you met her only one month ago. So don’t “go off the deep end” and marry her now.
Ex: I think he “has gone off the deep end” because he has been acting so crazy recently.
