I was on the outs with my girlfriend for a while, but now I'm back in the saddle again.
A good example in music is the sexy 1980's country music hit by Mel
Tillis, "I Got the Horse (i.e. penis) and She Got the Saddle (i.e. pussy)", with the chorus line, "together we're gonna ride, ride, ride!"
Another: In the movie Semi-Tough, when Kris Kristofferson finally gets the woman he loves, Jill Clayburgh, back in bed and is ready to fuck her (you can see his big hard-on poking up the sheets) the background music starts playing
Gene Autrey's 1940's
cowboy song, "I'm Back in the Saddle Again", as the scene fades.