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.