Horses will often spook in an arena, on a hack, or even around their yard; and sometimes for no apparent reason. The invisible monster that has so disconcerted them can continue to be a problem and a major frustration for you. The horse may pass by the same spot a hundred and more times and remain troubled by something that you simply cannot see or which is completely benign. Whether an object is real or imagined, it can be difficult to prevent your horse from spooking at it again. Whilst such a tendency can be amusing, it also presents a danger to you.
Your safety is paramount so it is important to address the problem but not to force the issue. You must remain vigilante and it is often best to dismount and work from the ground to see if your horse spooks again. Try avoiding the area where the spook occurred for a while and then gradually move closer to it throughout the session. If you are in the saddle, don't look at the offending object or area, look away. Encourage your horse to do the same. Don't try to pull back and remain calm. Any tension in your body will reinforce the tension that your horse is feeling. Make sure that you keep moving forward. Don't make any actions that actively encourage your horse to vary its line and gait. Remain committed to your horse's movement. If he does lurch, then go with him and do everything you can not to yank on his mouth. Your horse should stay on the right path even if he does spook but if he isn't looking at whatever has troubled him he should soon calm down. If you repeat this procedure your horse may eventually learn not to react to whatever is troubling him. But it might take many repetitions to achieve this. Always encourage your horse verbally and with a pat and provide a distraction after you have passed the moment of danger. Never stop after a spook and pat your horse because you will be rewarding him for the wrong behaviour.
Avoiding the Problem
If your horse continues in the same part of the arena, you might have to accept that you have to avoid it for a while. Ride elsewhere for a few days and then return to the scene of the crime. Your horse might have forgotten about whatever scared them.
Whatever tactic you try, don't get rough or angry as you will simply be reminding your horse that there is an issue. If you act like there is no problem, your horse should pick up on your signals. The more distressed you become about the situation, the more your horse will feel tense. If all else fails, ask someone else to ride your horse past the problem area just in case it is something that you are doing which is perpetuating the problem. If your horse still spooks, seek professional advice.