头脑清醒

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

山是危险的运动，你必须时刻头脑清醒。

A whiff of fresh air cleared his head.

他吸了一点新鲜空气后头脑清醒了。

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

如果想要婚姻美满，那么在步入婚姻堂的时候两个都得头脑清醒，知道婚姻意味着什么。