I've been riding a cob mare for about 7 months now. When I first rode her she was very forward going but strong. I like the forward going... and we have cracked the strength in the school she goes lovely in there now, but as soon as I take her in the field or into an arena it all goes to pot. She's in a snaffle. She has jumped most of her life and loves it, but the past few months she's started to refuse jumps and then canters off with her head really low... therefore I can't pull her up and it take me a good five minutes to stop her. Any advice? I'd love to take her to shows jumping but her refusing and then cantering off with her head low makes me nervous like I'm out of control, I really want to take her cross country aswell but I am not going just to be out of control!