头脑清醒

Mountaineering is dangerous, so you need to keep your wits about you.

登山是危险的运动，你必须时刻头脑清。

A whiff of fresh air cleared his head.

他吸一点新鲜空气后头脑清。

If a marriage is to work, both partners must go into it with their eyes open.

果想要美满，那么在步入堂的时候两个人都得头脑清，知意味着什么。