Just a few of MY thoughts after reading all the great advice on breathing, long tones etc. in the 20 posts above.
What is the goal of playing trumpet, flugel, cornet? Hopefully, to make beautiful music on an instrument you love to hear!
When you listen to a great player, do they move your spirit? The air on a G string as played on the flugel by Sergia Nakariakov, Trumpet concherto by James,
Louie playing and singing about "being Black and so blue", Chet Baker - You don't know what love is, all come to mind.
Maybe give yourself an attaboy break from all the necessary "work" of learning by doing the following.
Play your heart out on your favorite piece of music. Listen! Are you making music that you enjoy?
Not that it is perfect. That is what you are working toward. Do you not hear how much better it was than maybe 6 months, 9 months, a year ago.
Record yourself. Can you say, wow! That sounds good. I know you will find flaws, but did you "enjoy" playing and listening?
OK Now back to work!
BTW I really believe it goes much better when you are rested and relaxed.
I especially like the comment about ATTITUDE.
If you keep telling yourself you are bad, you will continue to be.
If you keep telling you are good and will be better you will be.
I don't know how it works with trumpet players, but it sure works on kids. I have a brood and ALL winners! As well as a nationally known Pipe Organ guy.