Jumpings something I've had trouble with since I had a period of about 3 months were at least once a lesson I would fall cantering jumps. All I can say is take the jumps lower I was jumping 2'6 I went back down to jumps under 2 foot and built my confidence up, after a LONG time I got to the point where I could canter a 2'6 - 2'9 course again and ENJOY it which was nice since I really stopped enjoying jumping for a bit, and the only thing that kept me going was I knew how much I loved it when I had confidence.