I was there myself for many years, SvV.

Greg explains it better than anyone I’ve ever seen.

What helped me the most was focusing in on the fact that less air is required the higher we ascend and we have a tendency to over blow.

I played a G below the staff, followed by a G on the staff with a breath attack. Both notes with passively released air. I paid close attention to how little difference in effort that octave was and imagined how the next octave, with even less air being required, would / should feel–how that G should feel. And I was willing to fail by focusing on the Process I wanted to experiment with–I wanted more to see how that Process would work, or wouldn’t (which is what I expected, frankly) than I wanted to hit the note. But the G did come out, and the A and soon thereafter the high C. Less air, softer not louder is what helped me get up there. When I do play loud up there, its more of an opening up of the aperture to let more air through faster than it is blowing harder, clamping tighter, etc.

It hasn’t been a straight sequential line upward of improvement, I have wanted to literally throw my instrument away and destroy it for good since playing my first High C a couple years ago…but I’m glad I didn’t. It hasn’t been easy and I can’t yet do everything I want on the trumpet, but I can play things I never thought possible for me and I understand better how the instrument works.

Greg is the best guide I have found, but he is only a guide–we have to own our own interpretation of how to play relaxed, efficiently, etc.

Its not a matter of playing exercises, but honing in on the experiences you are having while playing the exercises–what works, what doesn’t, what feels /sounds better, is our throat closed off / strained, etc.

My $.02 FWIW. Good luck–hope your “coffee moment” comes very soon! 🙂