Just remember that target panic is natural. The reason you found success early is because your subconscious has not yet learned the shot sequence and it is not shortcutting it yet. Eventually the subcon will attempt to make you more efficient by shortcutting what it can, like holding on target. It is the natural way our mind works. It is not that target panic went away on its own, the mind just forgot how to be efficient with the shot process. By efficient I don't mean good!!!! The prior advice to concentrate on form was good, more specifically, concentration should be placed on shot activation and let the subcon do the aiming for you.
Good luck