keep (one's) chin up
To improve one's mood, especially when sad or discouraged. Come on, the project was not a total failure—keep your chin up! Keep your chin up, honey—tomorrow's another day.
keep one's chin up
Fig. to keep one's spirits high; to act brave and confident. Keep your chin up, John. Things will get better. Just keep your chin up and tell the judge exactly what happened.
keep (one's) chin up
To be stalwart, courageous, or optimistic in the face of difficulty.