clear one's head
clear one's mind

"You'll need a clear head if you're going to find the right way to make the man pay."

But in order to face your problems, you need a clear head.

She would have a clear head and keep her focus.

He'd need a clear head over the next few days.

He needed a clear head for the next few hours.

Yeah, as if a clear head had done anything for us thus far.

If ever she needed a clear head it was now.

She needed to think this through with a clear head.

We need to look at it with a clear head.

He wanted to keep a clear head for what was coming later.