Let's pick any horse trainer's trainer. Clinton Anderson, Warwick Schiller, Buck Brannaman, Vicki Wilson, Stacy Westfall or (insert your favorite here). Now lets pick a horse to train following your favorite style.
If you have a the easy horse, it will just work. You will struggle less than others around you because you have the easy horse. But the easy horse isn't easy because he or she is easy. They are easy because you and the horse get each other in a way other horse and human combos don't.
Let me explain this another way. When a couple has a family, they have a parenting style. Some are loud and yell a lot. Others are soft spoken and gentle. As a parent the temperament of your child won't be known until it's known. Some kids shudder at a softly spoken no. Other kids test their boundaries again endlessly. When some toddlers fall down, they blame the ground. The parent has to constantly remind the child to look where they are going and, no, it is not the ground's fault. A loud parent who gets a child who needs to be spoken softly to, will always have a disconnect. Their temperament does not match their child's.
This happens with horses and humans too. Magic happens when a horse's temperament matches their human's. The horse is able to follow easily whatever the human does because the horse has been spoken to in way it understands. This eases the consequences for the myriad of mistakes of the learning trainer. Unfortunately, when other's seek advice from their group, those who flowed through the process lack understanding of the difficulties faced when you and your horse's temperament are not so well matched.
The person who wants to be soft and easy with their horse, but has a child who says "That was the rule yesterday. But has it changed today?" The constant testing can feel like failure. There are, of course, too many relationship combinations to explain. But I put this out there, that if you are struggling with your horse, it can help to understand your temperament and your pet's temperament. As the human (adult), you must find a way to meet the temperament of the child.