Instructions
Determine the underlying cause of your horse's barn-sour behavior. Refusing to go is a common sign of being barn sour and may be interpreted as being lazy; some horses are genuinely lazy, but others simply are afraid of leaving the herd.
Have an experienced rider or trainer attempt to ride the horse away from the barn. If the horse complies for the experienced rider, chances are that it is simply being lazy otherwise and knows that you do not have the confidence or experience to make it leave the barn. In other words, the horse has been getting its way by acting barn sour; the behavior has been rewarded and reinforced. If the horse is resistant to the experienced rider, the issue is a training one and you will have to retrain the horse to eliminate the behavior.
Ride the horse away from the barn with a group of horses. Some horses are more herd-bound than barn-bound and will ride away from the barn when with the herd. If your horse falls into this category, you need encourage the horse to be less herd bound by riding it alone more often, encouraging it to bond more strongly with you, and eliminating the herd dependency by turning it out alone.
Contact a qualified horseback riding instructor in your area and take some lessons to improve your riding skills and confidence. If your horse is barn sour only with you, then you need to improve your riding abilities to the point where you feel confident in your ability and able to make the horse listen and respond to you.
Practice riding the horse away from the barn. Give clear cues, and use spurs or a riding crop if necessary. Relax in the saddle and give confident cues, as your horse can sense it if you are nervous and will be more likely to misbehave if you are.
In extreme cases, you may need to have another person on the ground leading the horse away from the barn while you cue it from the saddle. Reward positive behavior with praise and treats (if desired). Make "away from the barn" a happy place that your horse will want to go, and then reward it for doing so.
How to Control Lazy Barn-Sour Horses
The term "barn sour" is used to describe a horse that misbehaves when ridden away from the barn or its herd mates. Often these horses are resistant to leaving the barn or try to run back to it when returning from the ride. When a horse is barn sour, underlying issues cause this behavior and should be dealt with because barn-sour horses can become dangerous if not handled appropriately.