Let me start out by saying - Dressage, Dressage, Dressage, Dressage and then some more Dressage after you've already done some Dressage. :P Seriously.
If you have a course with 10 fences, how many strides are there? 10 right, because you have 10 fences. Now, how many strides are there between the fences? Alot more, but to emphasise, that means that there is that much more time and space between the fences, to do what? Dressage.
After all, jumping is dressage with speed bumps.
Establishing Adjustability, establishing rhythm, roundness, lightness, your horse in their hind end, light to your aids. Establishing YOUR position, how to use your seat, your legs, your core, your body - before your hands.
Also remember, our horses reflect 100% of what we do in the saddle. So if you are stiff, tense - so are our horses.
Remember, if Grand Prix Jumpers spend up to 5 days a week doing only Dresage, and their horses can do minimally level 3 dressage movements - there's a reason.
Also, if you give your horse something to lean into, he will take it 100% of the time. Especially OTTB's.
I can only assume, because I cannot see video's of you riding, but it would be, that you are riding hands first. You cannot get any rhythm, adjustability or control by riding your horses face.
Forget your horses face, and focus on his hind end. Forget your horses face, and focus on getting him off of his forehand. Forget his face and focus on rounding him up into your aids and establishing a rhythm - how do you do this?
Dressage and proper body position to be an effective rider, to make your horse an effective mount.
Let me tell you my experience:
When I first started riding my now OTTB Nelson - he was great out on the trails, great in the Dressage Ring, but when it came to jumping, he was super powerful, very strong and extremely forward.
I remember jumping a small CC fence with him, and by the time I got him back down and under control, we were already clear over on the other side of the CC field. Rediculous.
So, at that time, Dorothy Crowell was coming to my barn for our Local Pony Club to give a Clinic *Dorothy is a CIC**** and CCI**** Eventer, who has represented the U.S.A in the Olympics* so I signed up to ride in her clinic because I wanted and needed help with Nelson's power over fences.
She set up a grid, 3 jumps * I cannot quite recall the striding now * but the first fence was an x rail I believe, to a 3 or 4 stride, to an Oxer, to a 4 or 5 stride and to a verticle.
Nelson and I approached the first fence quiet and at a nice rhythmic pace. The moment he landed from that first fence, he took off. That 3 or 4 stride became a 2 or 3 stride and the 4 or 5 stride became a 3 or 4 stride. I remember I was standing in my irons pulling on his face.
She stopped us and pulled us aside. The first thing she told me was "you give your horse something to lean into, he'll take it" and that is exactly what Nelson did. I pulled on the reins, he said "thank you!" took it and leant into it and was gone.
She taught me Seat Into Legs Into Hands To Soften.
Your seat controls your horses hind end. You establish a rhythm with your seat. You establish impulsion with your seat - you activate that hind end with your seat.
You tense your seat - your horse becomes tense. You relax your seat, your horse relaxes. You slow your seat, your horse slows down to you. You quicken your seat, your horse quickens.
It comes from your seat. You must learn to ride on all 3 points *two seat bones, and crotch*
Remain over his center of gravity. Do not lean forward, do not lean back - remain over his center. You cannot allow your seat to lock, it has to be fluid and soft.
The moment you get what you are asking for from your seat, you activate your legs. Your legs continue that rhythm you've created through your seat, and your legs lift the horses ribs/spine up into your seat.
Your hands come into play lastly. Your outside rein must be there to allow that energy to recyle. You do not want that energy to gush out your horses front end. But they are soft, supple and must be giving at all times.
I was shown this by Dorothy and I immediately had a different horse.
She had me approach the first fence, when I was a stride away, she had me release my arms, sit and close my legs. The moment we landed I had to sit back down, slow my seat down, close my legs and rock him back through my upper body and core. Then a stride away, I released my body and allowed the fence to come to us.
If he tried to speed up at all, I was to make him to exercises - whether it be figure 8's or serpentines or circles, I had to work on slowing my seat down, lifting his ribs and bring him back down under me.
Then we would repeat the fences.
Learning Adjustability is very important on the flat first, before you jump.