Actually, altering my grip is one change I've already made since starting lessons with my teacher. I now use only my thumb and index fingers to support the trumpet with my left hand and the other three go under the third valve slide. I've also tucked my right thumb between valve casings 1 and 2 and taken my pink out of the pinky hook. I don't worry too much about the naturally sharp notes that require the third slide to be kicked out. I find that this gives me less leverage to push the horn into my face, and is a sort of sanity check when I desperately want to press harder.