lighten up
Become or cause to become less serious or gloomy, and more cheerful. For example, Lighten up, Sam—it'll turn out all right. This slangy expression transfers reducing a physical weight to a change of mood or attitude.
Words nearby lighten up
light-struck,
light-year,
lightboard,
lightboat,
lighten,
lighten up,
lightening,
lighter,
lighter fluid,
lighter than air,
lighter-than-air