It is often said that horses live in the present. This is true. However horses also have the best memory of all domestic animals.
The way your horse responds to something today won`t necessarily be the way he/she responded yesterday.
Our horse, Bob, has always been very easy to trailer load. Yesterday he did not want to get on the trailer. We have learned that everything means something and nothing means nothing. We found that the door to the upper storage area at the front of the trailer had been left open. So Bob could see this nice big cave that was a perfect hiding place for a cougar or even the notorious and deadly sabre toothed butterfly. There was no way he was going near that scary place. We closed the door and led him on the trailer. The lead on was important because he trusts us and as long as we were leading he was okay with following. We let him stay on the trailer and we stayed with him while he carefully checked everything out. We took him off and did some ground exercises and then repeated the lead on and rest. We did this several times over the next hour. By the end of it he was okay with getting on the trailer.
What happens tomorrow? I don`t know. I hope all will be okay, but, if he has an issue we will respect it and help him through it. There is no doubt that he will remember the scary moment yesterday but he will also remember that nothing bad happened. No matter what keep the horse`s trust and maintain your leadership.