"Put on a brave face" is to express that someone try to hide it's feeling and pretend to be alright. What if someone tries but fails, can I say, "He lost his brave face after that"? Or what would be a better word or phrase to express this situation?
What if someone tries but fails .. What would be a way to express this situation?
Well, that depends on a few different factors, such as
- How brave was this person to begin with?
- Was this person humbled when he failed? Or did he simply become less brave?
You haven't supplied too many details about the scenario, so there is room for some interpretation. I'm assuming that this person wasn't very brave to begin with (based on how you said this person will "try to hide feelings and pretend to be alright"), and that maybe everyone else thinks that some humility came with the failure (otherwise, you might have inquired about "I lost my brave face" instead of, "He lost his brave face").
So, I'm assuming that that this person is thinking pretty highly of himself when he puts on his "brave face," but you want to describe his feelings afterwards, when that bravado is proven to be hollow. So long as those aren't inaccurate assumptions, here are a few idioms you might consider:
that took him down a peg or two (according to NOAD, this means make someone realize that they are less talented or important than they think are. Sometimes the word notch is used instead of peg)
that wiped the smile off his face (according to Cambridge, this means to make someone feel less happy or confident, especially someone who is annoying you because they think they are very clever)
that served up a big slice of humble pie (according to Yahoo's online dictionary, eating humble pie means admitting one's faults in humiliating circumstances)
he was all talk and no action (this can be used when someone boasts a lot, but, when crunch time comes, the person folds under pressure)
he was apparently too big for his britches (or breeches; according to UE.com, this means a person is conceited with an exaggerated sense of their own importance; this one might be a stretch)
Most of these idioms focus more on the humility that accompanied this person's failure when they "lost their brave face." If you'd rather focus on how the person became less confident instead, you could simply say, "He lost his courage."
I agree with Bill Franke that a form like “He put on a brave face, but he lost it when he got scared” is acceptable; but “he lost his brave face when he got scared” is less acceptable for several reasons. Perhaps the most important is that because it isn't idiomatic, people may interpret it literally, and may envision the person actually losing his face, as opposed to merely changing expression from brave to frightened.
Among many words pertaining to a change from brave to scared or up to down are
• downfallen, “Pertaining to one who is crestfallen, depressed, down in the dumps”
• crestfallen, “Sad because of a recent disappointment”
• shamefaced, “ashamed, displaying shame, especially by blushing in the face”
• abashed, meaning “embarrassed, disconcerted, or ashamed”