Keep your chin up! - 保持乐观！

Idiom: keep one’s chin up

Definition: to stay positive

Examples:

1. Even when she was unemployed, Emma managed to keep her chin up.

2. Keep your chin up! You’ll be good at English soon.

中文解释在这里：:http://www.youzienglish.com/index.php/cn/idiom_of_the_day/