out of (one's) mind
slang Crazy. This phrase can be followed by "with" and the cause of the craziness. He's out of his mind if he thinks this plan is going to work! After yet another sleepless night, I'm starting to feel like I'm out of my mind with exhaustion.
*out of one's mind
and *out of one's head; *out of one's sensesFig. to be silly and senseless; to be crazy and irrational. (*Typically: be ~; go ~.) Why did you do that? You must be out of your mind! Don't drive so fast, Tom! You have to be out of your head!