清醒(qīng xǐng) - awake, sober, clear headed in Mandarin

清醒 (qīng xǐng) is the state of having your wits about you. It runs from the plain physical sense, awake rather than asleep or drunk, right through to the figurative one, seeing a situation for what it is.

Note that it is a state, not an event. 醒 and 醒来 are the moment of waking; 清醒 is the condition you are in afterwards. 他醒了 means he woke up, while 他很清醒 means he is alert and thinking straight.

The trap is treating it as a bare synonym for awake. Someone can be 醒着 (awake) and still half asleep or three drinks in, and calling them 清醒 would be wrong. The word carries a claim about the quality of their thinking, which is exactly why 清醒的决定 works and why 保持清醒 is as much a warning as an instruction.