The first car I ever drove was a 1991 Ford Telstar with a manual transmission. At first, I was terrified of grating the gears, stalling, or simply not being able to move at all except in mortifying bunny-hops. After I'd figured out how to use the machinery, I realized that what frightened me more was steering the thing, parking it, judging how much space I needed to change lanes on the highway, and that sort of thing.
My instructor was a cranky elderly lady who was fond of reciting "Remember the six positions of the two-car crash!" as I clutched the steering wheel with white knuckles and tried not to hyperventilate. "Check your mirrors! You forgot to check! Never forget to check! Look behind you! No! In front of you!" The poor thing probably had permanently high cortisol levels from all the things her students did on the road. But eventually I was able to stop grating the gears, internalize the rules of the road, and pass my test (on my third attempt... hmm).
I thought fondly of my driving the instructor recently when I was on a visit to a high school orchestra. The teacher had done a great job of instrumental instruction and aspects of musicianship such as complicated rhythm. But I noticed that the majority of the students were buried in their music stands, barely looking up but for the conductor's cues. As a result, the ensemble's attacks weren't unified and the tempo got slower and slower.
And it occurred to me that playing in any ensemble isn't unlike learning to drive a car. Once you've mastered the task of playing tolerably well and have practised your part and studied the full score so you know "how it goes," when you get to rehearsal your gaze needs to be moving constantly. Of course you're going to look at your stand, but you constantly have to glance at the conductor, the concertmaster, the section principal, and so on. You have to be able to memorize short passages from the score so you can look up to give and observe cues without losing your place. It's as if having mastered how the gears work, now you have to make sure you're looking at the road in front of you, potential hazards in the distance, the rear-view mirror, the side mirrors, etc, with only occasional glances at the speedometer to check you aren't over the limit.
Successful driving and successful ensemble playing depend on having learned to do the thing in itself, i.e. master the equipment, so that it becomes automatic and you're liberated to do more things. If someone breaks a rule of the road and makes a mistake, alert and adept drivers can often adjust their own driving to avoid accidents. Someone comes in wrong in an ensemble? If everyone else is alert, adept at their own part, and knows the score well, they can "save" that person without having to stop.
Making music is inherently exciting. It's like driving down the freeway at high speeds, changing lanes, passing other vehicles, knowing where you're going, dodging hazards. If you can do the same thing in an ensemble -- get your head out of the stand and your gaze constantly moving -- you'll get to your destination much more smoothly.