What do each of these have in common? Bowlers, pitchers, batters, swimmers, golfers, tennis players, quarterbacks, soccer players, car drivers, and even old guys pushing grand kids on swings? The same thing that a trumpet player should have as he/(she) begins a phrase: Momentum.
Bowlers take steps before releasing ball bringing it backwards first. Pitchers wind up, swimmers jump/dive, golfers take back swings as do tennis players. Quarterbacks can do it fast. Soccer players likewise need to begin motion before contact. Drivers can't hit 60 mph in a split second. Even grand dads instinctively build momentum as the swing goes higher.
Yet how often we trumpet players start passages with virtually no prep, only a flat-footed stab in the dark. Quickly we are out of gas.
On the best of days, this is usually not an issue. It is the pressure situations that tend to freeze our natural approach to playing. Too little attention to starting mechanics, and results are predictable: a bad back from inordinate stress, notes that forget to speak, etc. You know how it goes.
Before fall classes, lessons, and ensembles start up in full swing, take time during each practice session to visualize several of these pictures. Make a habit of taking in and releasing the breaths that are needed. A putter doesn't need to wind up like a fast ball pitcher, obviously. Work on this. You don't need twenty text books. It's not rocket science, just inhale and exhale in time.
Mental concepts are great. Maybe even a room full of posters of sports heroes in their moments of glory could have a positive effect on your playing. Mental prep builds confidence.
In the CSO, some of my colleagues had pictures on the inside of their folders for inspiration. One had a sizzling picture of Maynard busting a gut on some high note. Another colleague had a mean pic of himself ready to do some serious damage to the viola section! Whatever it takes!