There was a lot to be learned, but what stuck with me the most was from the second ride. It was a friend of mine and her paint mare, both of whom have come a long way since meeting each other. That being said, the mare has always been difficult, especially when it comes to contact, but it's become worse recently and has led to some more obvious resistance (small rears and bucks). The first reaction in this case is to simply ride through it. Send the horse forward, guide them to the hand, yadda yadda, but of course it goes beyond that. Neither the mare nor Miss El were happy with the whole send them forward thing, so other causes were considered.
There are a number of different reasons as to why a horse would completely resist contact. Tack fit in general was questioned, as well as the type of bit, status on teeth, past training, and also a recent chiropractor who may or may not have known what she was doing.
In the end it came down to a few different issues. Most of the mare's training was done by the girl, and she admits that the problem is mainly due to her own inexperience. The chiro's usefulness was also questioned. Then there was also an issue of stiffness, which I personally saw in the lower neck and lumbar vertabrea/sacrum, but then again, I don't know what I'm talking about and had to look up those last two terms. I'm still learning. It's a process.