We squeeze with our legs when we want to stay in the saddle instead of relaxing them and allowing them to drape fully around the barrel of the horse. When we want the horse to stop, slow down or when we are tense, nervous or need balance we pull back on the reins.
All of these things are against the nature of the horse. To stay in the saddle best is to sit upright or slightly behind the vertical which helps to plant you in the saddle rather than creating ripe conditions for a catapult when you lean forwards. When we squeeze our legs it helps only to push us out of the saddle than to hold us in it. And when we pull backwards on the reins we incite the horse to move into that pressure by leaning heavily on the bit and to move on the forehand.
Every action of the hand must be executed with intelligent thought because without it we are left only to our ape-like instincts and to pulling backwards on the reins.. or pulling sideways. The most effective actions of the hand are: left to right, right to left, up to down, down to up. Executing these directions in a circular motion only helps to increase their efficacy and to relax the mouth of the horse when he is tense.