I have a horse that is very mistrusting of people on the ground. It took me a long time to get him to trust me, but I feel like he truly does now. I spend a lot of time with him that is not related to work...stuff I think he likes to do, like hand grazing, grooming, petting, going on walks, getting treats. Don't quit working him though. You have to keep him well balanced with love and staying respectful. I have crossed the line before and let my boy get a little pushy, but when that happens you just have to realize your mistake and balance things out again.