It all comes down to air-flow, regardless of how you approach it, whether from the point of view of yoga or pilates or the gym teacher's suggestion for crunches and situps, or from other people's suggestions about this that or the other approach to breathing for playing the trumpet. How you get to the ideal air-flow is less important than the fact that you need to get there. If your current mind-set is somehow preventing you from doing it properly, change the way you think about it and forget the people who say "don't think about it that way, think about it this way." Well, if you're already thinking about it "this way" and it's not helping you, then think about it "that way" despite the advice against it. Air flow, pure and simple. If it's correct, you can play anything, if it's not correct you can barely play at all. People throw around a lot of discussion about the diaphragm and its part in the breathing process -- everybody should do their own research into just what part it actually plays in the breathing process and how we control it. There is a lot of information out there on the web about it, and some sites seem to contradict other sites as to just what muscles actually are what we breathe with. Just as with the discussions on breathing for playing the trumpet seem to contradict each other -- the real truth is that they're all correct, just not correct for everybody, since everybody's body is different. And the more we each of us educate ourselves on how the body works and try to come to an understanding about how our individual body works, the better off we'll be rather than listening to people say "Do it like this, it will help you" while others say "don't do it like that, it'll hurt you." Basically, we're all born with perfect understanding about how to breathe, and then as we learn more we obsess about it way too much. To play the trumpet, you inhale then you exhale in a more forceful way to get the lips to make the air in the trumpet vibrate. Now get your horns out and experiment until you find the best way to breathe so you can play endlessly and get the tone you want along with the range you want.