clear one's head
clear one's mind

He needed a clear mind for what was to come.

And better that she meet her fate with a clear mind.

It took a woman, the cold blood and clear mind of a female.

Because what comes with health is a clear mind and a high spirit.

I want to go into everything with a clear mind.

The answer was there in his mind, clear and disturbing.

I need, at the very least, to have a clear mind and to be seen to do so.

He said a clear mind allowed him to reach his decision.

I need a clear mind and a good night's sleep.

Better to have a strong clear mind for what happens.