>I have finally quit denying reality and I have to admit to
> the condition of ... High Note Anxiety.
There are two different issues here. One is how to increase your range so the B is not within the anxiety region. But then you'll want to do Prince of Denmark for some cousin's wedding and you'll be right back in it with a C# (on the Bb trumpet); then comes all the Baroque stuff for D trumpet and you're at an E; etc.
There is lots of advice, good and bad, on how to increase your range. If the note just ins't reliably there, you are playing too hard a piece at this stage of your development.
But if the note is there under the circumstance in which you are going to be playing -- say just one time through, perhaps after a hymn to use as a warm-up and intonation check, the problem is not technique but genuine high note anxiety. That high note anxiety is really form of stage fright and is something you need to confront on that basis. Saying "it's just mental" doesn't mean it isn't real. It definitely is real and can really mess-up a trumpet player. You know the note is high and exposed; you get nervous; you tighten up; the air flow is reduced; you don't blow through it and the note clams. That's real. But, being the result of an initial mental state, a mental appoach may reduce the problem. There is at least as much advice on stage fright as on embochures because the problem is not limited to brass players.
What I do with an isolated high note at the limit of what I can play well (as opposed to a piece that goes up and stays there) is to love the note, anticipate it as the climax of my performance, relish the opportunity solidly to stick it while listening to the hall reverberate back. The B in "Prayer of St. G." is in the kind of phrase where this mental game will really work well for me. During the rest before that phrase the organ has been playing a line of half notes that get gradually higher and louder until your enterance. Listen to the organ's build of range and volume and marvel at the increasing sense of sound and power. Think about the drama of duplicating that wonderful crescendo with the brillance of the trumpet. You enter forte on a C# and build; into the fourth measure you have a pick-up C# to the E and crescendo, then the E to the A. The F# to B is the same interval, listen to the interval as you play the E to the A. The music gives you a chance for a breath (by the way the organ does not have a moving part at this point -- you can take your time with that breath) and lets you add power to play ff. THIS IS YOUR MOMENT. Don't worry about the B -- BLOW THE B. WOW!! That was good.
The one that comes later is in a moving line and is easier and the confidence from the one I just hit will ward of the anxiety for it. I'm going to play it just the same to remind the audience of how beautiful the first one really was.
This is a game. I know it's a game but it still works for me. Most of us want to play at our upper limits. If you didn't WANT that B, you could play the Sullivan's Lost Chord with a G on the top of the staff for a high note. You want it; so TAKE it.