The main problem with punching is that you are USING your "big muscles". Therein lies the problem. You are giving yourself time to "panic" so to speak. The thing with hair triggering is the fact that it's so quick you don't have time to punch or pull. With the thumb on the back of your neck and hand relaxed, you can feel if you are creeping forward or pulling back. This little bit of extra sensory input will help your form become more repeatable.