Definitely figure outfor sure if it's your error or your horse's before you try anything differently. My horse started rushing to jumps in October, and because I didn't have time to take any lessons with my fall sport, I automatically blamed myself and tried to fix the problem without a second party. To say the least, no matter what I tried differently I absolutely couldn't figure out what I was going wrong so I just learned to ride out her crazy jumps like nothing until about a month ago when I had time to take a lesson. As it turns out, it was a little bit of both me and my horse. My trainer immediately noticed that Lena was over anticipating the jumps, and in effect decided 5 strides ahead of it that the only way that she could get over it was to rocket towards it. So it wasn't really my fault to start, BUT I was fueling the fire by becoming frustrated with her, so I would tense up a few strides before the jump, and she would feel that and think "JUMP TIME!" and take off like a big crazy.
Here's how I'm fixing the problem. (Yeah, she's better but there's always room for improvement) In the arena, I set up a vertical (between 2'3-2'9 for Lena, because she takes 3' like cake) along the shoulder of the rail, and I leave enough room on the rail to confortably canter inbetween the jump and the edge. I only use about half of the arena to canter in a nice 20 meter circle, passing the jump each time which is strategically placed at a point in the circle where if I decide to take it, I can just turn her into it and take it in about 2 or 3 strides. (ie; the jump has to be close enough to your "turning in spot" so that your horse doesn't think about it.) So, when I get a nice relaxed canter out of her a for few circles I randomly point her into the jump, without changing anything about my position or on her. The first night I tried this she got it after about 3 tries.
The main thing you have to pay attention to with this is that you maintain a constant, relaxed position. I ride in 3-point but have to sit on Lena's back 2 strides before the jump so that she uses her butt to push off, but I don't DRIVE her to the jump, give her leg, kick, nothing. So when I approach the jump in this exercise, I just lightly sit back and lightly pop up and down in the saddle and then fold when she takes the jump.
If you want me to doodle a diagram of how the arena should look I'd be more than happy to.