A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

keep one’s eyes open • open someone’s eyes
keep one’s eyes open —be watchful and alert: During the three
weeks I stayed in Dar-es-Salaam, keeping my eyes open, I was
hard put to find evidence of Chinese influence.
open someone’s eyes —make a person acutely aware of the truth
of a situation: Attending Harvard only served to open her eyes
to a whole new range of inequalities that exist in society. Cf.:
eye opener — a startling or shocking revelation: It was a real eye-
opener for the adults. The ease that the children displayed
with the technology was enough to amaze even a veteran.
See also: with one’s eyes closed / with one’s eyes open.
keep one’s face • lose one’s face
keep one’s face —(also: keep a straight face) refrain from show-
ing one’s feelings by one’s facial expression: The performance
was so absurd that I could hardly keep my face.
Note: 
The expression does not correlate in meaning with the
phrase save one’s face—(also: save face) avoid being disgraced
or humiliated: If he represented a first-class paper and wished
to “save his face” he had better travel in state.
lose one’s face —(also: lose face) damage one’s reputation; lose
people’s respect: He is such a powerful and important man he
can not afford to lose his face.
keep one’s feet • keep one’s feet on the ground
keep one’s feet—keep one’s balance; remain standing: As he
was leaving, he stumbled on the stairs but was able to keep
his feet.
keep one’s feet on the ground —(also: have one’s feet on the
ground) have a sensible and realistic attitude to life: When the
other band members tend to lose touch with reality, he makes
sure everyone keeps his feet on the ground.
keep one’s hair • keep one’s hair on
keep one’s hair —not become bald: He considers himself to
have been lucky during the early stages of the disease: no sick-
ness, and he kept his hair until quite recently.
keep one’s hair on —(coll.) not lose one’s temper; remain
calm: His annoyance evaporated in a grin. “You’re right. She’s
got a tough job. I’ll try to keep my hair on in future.”