He was boasting about how brave he was at the start, but copped out (of it) at the finish.
他起初夸耀自己勇敢,到头来却打了退堂鼓。
He's always boasting about his children's success at school.
他总是夸耀他的孩子们学习成绩好。
It is of no use boasting of being rich on a desert island.
在无人岛上夸耀富有也是白费力气。