i started doing this a few years ago, the reason i think it works is due to the fact that emotions only last for 90seconds, the only reason the last longer is because you feed it/reset the 90sec timer every time you think about it. so focusing on the physical sensation in your body combined with the breathing is able to take your mind off whats actually making you feel the emotion for long enough for it to fade fully. ik this is a long comment but this is my understanding behind the mechanism of the technuiqe your explaining.