Spurred to Victory is an Playstation 3/Xbox 360 Achievement that is worth Bronze Trophy/10 Gamerscore.
Spurred to Victory is a secret achievement. It is not very difficult to obtain, though the player must be careful as to be aware of their horse's condition at all times.
In order to obtain this achievement, play from the beginning of the game. Shortly after a few missions, you'll receive the mission "Wild Horses, Tamed Passions" at MacFarlene's Ranch. After completing this level, you'll receive a Kentucky Saddler, one of the most strongest and fastest mounts in the game.
From this point on, simply play through 20 story missions without switching to a new horse at a hitching post. An easy way to prevent yourself from making the mistake of switching horses, is to just always ride on your own horse. If you're not sure as to if it is your horse or not, whistle before riding on a horse. Ignore the horses that NPCs offer you. Just whistle for your horse even if there are other horses around.
When you're engaging people in firefights, leave your horse behind. If your horse dies or if another horse comes at your whistle, reload the game from your last save. It may not be a bad idea to save twice after every mission to have a backup file in case something goes wrong.
