lose heart

Not for a moment did the brave man lose heart or suffer himself to grow weary in his difficult task.

I felt that if I thought the matter over I might lose heart, so I suddenly bounded into the arena.

But don't you lose heart, Jim, for I'm sure this isn't the end of our story, by any means.

A young soldier must not lose heart because he finds he is a prisoner.

But weeds have this virtue: they are not easily discouraged; they never lose heart entirely; they die game.