Let's face it. The lure of being in pursuit of an orchestra job is huge. Great literature by stupendous composers, an opportunity to play with fine players, conductors and soloists, and, in a lot of cases, a very good stable well-paying job or a good-enough-to-live-off-of job. Because of these opportunities, many music schools and conservatories want to be training grounds and factories that 'crank' out fine symphonic products.
That is all fine, except when the focus on a rigid, formularized approach to the orchestral literature goes into hyper-drive over the basics of rhythm, pitch and sound-evenness, in place of feeling the character of the whole piece where the excerpt is a part of it. Not just a bland, understated color or texture, but a living active piece of the whole musical organism. You cannot see the spleen or colon from the outside of the body, but without them playing their parts to the fullest, you would physically be in BIG danger. That, of course, could be said of other parts in the body and it can be said for all the players in the orchestra, where the individual players are the cells and the sections become molecules and organs.
I have heard many players develop three fundamental side effects from an imbalanced emphasis and approach to orchestral excerpts. They are:
A condition that is very mentally obsessed with orchestral excerpts to the point where it takes up almost all their practicing and when they listen to a piece all they can hear are their instrument's excerpts. It is usually a juvenile stage. (I experienced it myself to some degree and it is OK for a while in our growing years of excited enthusiasm; however, I have seen it continue in some, well after the point.)
A state where the player gets all tight and dull with the performance of the excerpts. It is an 'inflamed' condition and exaggerates rhythms and articulations to make sure they 'happen' and has very little real musical connection. The result can be very academic and robot-like and usually carries some contorted physical characteristics while playing the excerpts or before starting them.
This is a fear of excerpts. This can, in its advanced stages, cause real anxiety in the person who suffers from it just by hearing an excerpt. It makes a person freeze up and get very nervous if they actually have to play an excerpt. If the person did not know it was an excerpt and came across the music in an etude book, they could probably play it much better, due to the lack of the mental head trip they have gotten themselves into.
Some ways to prevent the 'itis' and the 'phobia' is to aways realize excerpts are pieces of a larger work and it is important to feel the surrounding music while you are playing or practicing your excerpts. Being able to play them in at least 3 different convincing ways makes it easier to not fall into deep ruts. Make sure you have your own personal musical connection to the excerpt and the piece as a whole beyond any theoretical or historical knowledge or understanding.
Moving beyond Excerpt-mania usually comes with musical and emotional growth. I f you feel stuck on having a fixation on excerpts, listen to other music that doesn't have your excerpts in them and expand your musical palate and build a relationship with music independent of excerpts or orchestral music.