From what you said, I would say that you have been training yourself to flinch, and doing a pretty good job of it. What you need to do is to train yourself not to flinch.
Let’s say you’re training a dog to come when called. Are you going to accept it when the dog doesn’t come? How well does it work to get mad or unhappy when the dog doesn’t come? The dog doesn’t like it when you’re mad or unhappy, but it doesn’t help him to learn to come. In fact, the dog might prefer to stay away from you when you’re mad or unhappy with him. No, what you have to do is something to change his behavior. Every. single. time. he doesn’t come. You might try beating him, or yanking on a long leash, rewarding him when he comes, or a combination of things. Some techniques might work better than others, and better with some dogs than with other dogs. But the basic rule remains the same: it is never an acceptable outcome for the dog not to come, not now, not for the rest of his life.
The same thing applies to your flinch. A flinch is never acceptable, starting now, for the rest of your life. Of course, you are still going to flinch, unless you are better than the best archers out there, but it is never acceptable; you have to do something about it. The best thing to do about it is to let down the bow and start all over again. It is better to have 20 let downs than one flinch that gets away from you. It’s like staring down the dog for a half hour with a treat in your hand rather than just walking away and letting him get away with not coming. Don’t try to train the dog to come unless you’ve got the time to follow through with it. Same thing with a flinch: if you let down every single time you flinch, you’re training your body that the response to a flinch from now on will be a let down and not a shot.
A second way, not recommended by most coaches, would be to recover from the flinch and carry on with the shot. I’ve seen champion archers do this successfully in tournaments, but those are people who don’t flinch very often, so are probably not training themselves to flinch when they recover without letting down. They are able to put the flinch out of their minds and continue with the shot as if it never happened. But for a person who flinches a lot, it would be better to train themselves to let down after a flinch. It is not an easy thing to let down when you’re primed for a shot, and it requires some training so the shot doesn’t get away from you after you flinch.
The third way would be to go through Jim’s course. Flinching is not exactly the same as target panic, but his course focuses on executing a perfect shot in a controlled environment. Because of the absence of any pressure, it is generally possible to go through his course without experiencing target panic. After repeating many hundreds of draws and shots without target panic, the target panic seems to stay away, hopefully forever, and the same might be true of your flinching.