I got this Phrase from one of my American teacher.
"Happy Trails" was the theme song for a radio and TV program in the 1940s and 50s. The program starred Roy Rogers and Dale Evans. This was a show about cowboy life. "Happy trails" meant "have a good time riding your horse on the trails."The song was always sung at the end of the program.
Happy trails to you, until we meet again.
Happy trails to you, keep smilin' until then.
Who cares about the clouds when we're together?
Just sing a song and bring the sunny weather.
Happy trails to you, 'till we meet again.