get on horse
get on (one's) horse
To prepare or get ready to leave. Well, I had better get on my horse. It was lovely to see you, as always. Time to get on my horse—I don't want to miss my train!
get on one's horse
Sl. to prepare to leave. (Usually fig., with no horse present.) It's time to get on my horse and get out of here. I've got to get on my horse and go.