I spent some time with a new horse, an Arab mare about 5 yrs old and just recently started. She's a rather spirited left-brained extrovert from what I could tell. She sure liked to move her feet and at first, I had a little trouble convincing her that it wasn't necessary. The owner was looking to get her into the trailer for her 3rd or 4th trail ride. I was looking for the mare to tell me she'd be ok with that.
But first, she needed to understand how to be around people at the end of a lead rope. She's a nice mare, but she hasn't been taught much about manners or having respect for the human nearby. So, we worked a little on building a language and me establishing some leadership. I wanted to teach her to lead nicely and I wanted her to start yielding to pressure at the poll. That was interesting - when her feet got stuck, I'd add pressure in Z4 or Z5. With the pressure from behind, she'd go jamming out in front, so I'd have to ask her to get back behind me. Then we'd go again...
She learned, there's no question. She was ears forward, licking and chewing, dropping her head in submission, all good stuff. I wanted to work on her confidence more. We played a bit more after I felt like we were starting to communicate and then I took her near the trailer so she could tell me how she felt about it. She said, loud and clear, she was not ok with the trailer! She pooped, lost her cool, ran around, called to momma (who was 20 ft away). I felt sad for her, she'd been trailered a few times already and she was obviously forced into it those times. I tried to explain that to the owners and hopefully I got my point across.
Just because a horse will do something, does not mean they are willing. There very nature makes them want to do what gets them away from pressure and that's what gets us into trouble. We have to listen when they tell us they aren't ready. And it's up to us to help them be ready for what we're asking.
In the end, I never asked her to load. I asked her to be ok with playing near the trailer and we accomplished that. Then, I had her owner take her and try a few things. That went well as her horse was much more calm now and had a clear understanding of what she was being asked to do.
It was, in my mind, quite successful!