May not sound like an achievement but I managed to do the exercise from the Pradipika where you squat on the front soles of your feet, hands on the floor and pull your abdomen inwards, all the way until you throw up. Activating this reflex and taking control of it is a fundamental of correcting how the body works. If you can't activate this function at will, you also cannot create the reflex where doing it accidentally feels wrong. You have to make mistakes to be able to do it right.