It sounds like a big part of the struggle isn't that you don’t understand what’s happening, but that you expect yourself to be able to stop it right away once you do. There is a gap between knowing and doing, and that gap is where the work actually happens. Your body is still learning something new, and learning takes repetition, not pressure. Each time you notice the feeling, even if you still react, you are already changing the pattern a little. The goal is not to stop everything at once, but to stay with yourself just a little longer each time.