"装开心"的意思是尽力保持快乐的心情，可以用英文表示为 "try to be happy" 或 "attempt to be happy." 这个短语源于中文，并不是英文原本就有的表达方式。

下面是一些英文例句：

I try to be happy every day. (我每天都尽力保持快乐的心情。)
She always tries to be happy, no matter what challenges she faces. (她总是尽力保持快乐的心情，不管面临什么挑战。)
He attempts to be happy by surrounding himself with positive people. (他通过身边聚满积极的人来尽力保持快乐的心情。)

这个短语也可以用来形容一个人，表示他/她总是尽力保持快乐的心情。例如：

She's always so cheerful and tries to be happy no matter what. (她总是这么开朗，尽力保持快乐的心情。)
He's a naturally happy person and always tries to be happy, even when things aren't going well. (他是一个天生快乐的人，即使事情不顺利也尽力保持快乐的心情。)