In the beginning, NOTHING seems natural about playing trumpet. That is why a teacher can be a great help. To learn the unnatural stuff, we need first of all to KNOW that we are doing it RIGHT, then the teacher needs to HEAR that we are practicing what is necessary ENOUGH. Grabbing a big breath when the body is not ready (crappy posture) just means that we throw ourselves into a high tension state and nothing works the way it should. Body use and breathing are tied together. After that, body, breathing and playing are tied close together, a big breath without our brain, ears and face prepared also lead to high tension. Getting those things sorted works best when someone in the know is guiding you. Reading badly qualified advice makes me think that the internet is one of the WORST places to get help. Too many people just interested in blogging anything that they may have heard. Some even lie and say that they "tried it".