From Longman Dictionary of Contemporary Englishput on a brave face/frontput on a brave face/frontPRETENDto pretend that you are happy when you are really very upset → brave
Examples from the Corpus
put on a brave face/front• He was shattered, though he put on a brave face.• I suppose parents have to put on a brave face.• Leaving the court the families all tried to put on a brave face.• Newspaper staff put on a brave face.• No one said a word all of us were consciously putting on a brave face.• Whether in denial or putting on a brave face, the delegates professed to be unperturbed by those numbers.• Meanwhile, Llandundo put on a brave face yesterday and struggled to get back to normal after last week's devastating floods. 