I wonder if you are perhaps riding with too much tension in your shoulders, arms, hands and fingers. Try relaxing all these muscles so that the bit floats softly and moves with the horse. If you tense all these muscles, the bit ceases to float with the bit, and the horse will continually run into it, which is uncomfortable and annoying for him/her. If you are riding with these muscles correctly relaxed most of the time, you should be able to “drop a cement wall in front of the horse” just by abruptly tensing all these muscles from a relaxed state to a fully tensed state. Once you have figured out how to control the tension in these muscles, you can also learn to tense groups of muscles, depending on how much increased tension you need to get the horse’s attention. Closing just your fingers tighter should be enough to slow the horse down, adding the hand muscles if he ignores you, and adding additional groups until he learns that ignoring increased finger tension will progress to the other muscle groups if he chooses to ignore the the increased finger tension. This method can give you much more (and virtually invisible) control, and once the horse figures it out, a much happier and more comfortable horse because you will be riding most of the time with much less contact.