idiom
a brave face
pretendirovat' byt' muzhestvennym, kogda na samom dele ty napugaesh'sya ili bespokoish'sya
Meaning
to pretend to be brave when you are actually scared or worried
Example
She put on **a brave face** despite feeling nervous inside.
Ona odela **mujestvennoe litso**, khotya ona chuvstvovala nervoznost' vnutri.