Here's one that was a bit of a major epiphany:
I was raised (by various music educators over the years) to believe that a professional musician should be so comprehensively equipped skills-wise that they can play any kind of music... a gig is a gig, and a pro is someone who Gets The Job Done, whether it's playing jazz standards on a yacht for a corporate fund-raising party, Broadway showtunes in the theater pit, post-Darmstadt total serialism in a Julliard recital hall, or Yoruba folk tunes at a coming-of-age ceremony in rural Nigeria. You're the bass player? You should know enough about music and be competant enough on your instrument and in your ears that you can do all of those gigs equally well.
And what I came to realize after about the first 20 years of working as a pro is that playing music is about so much more than just Playing The Right Notes At The Right Time. Playing music well requires understanding context and culture and history and ritual and how people integrate those things into their lives and how that integration has evolved over decades or centuries. Playing music well requires a connection to that integration that transcends the mechanics of simply extracting a tone from your instrument at a specific moment in time.
Sure, hand me the chart or give me a tape in advance and I'll show up to the gig and Play The Right Notes At The Right Time, because I'm a pro and pros Get The Job Done. But there are some musics that I have absolutely no connection to culturally, historically, ritually; they're simply not integrated into my being in any sense...and so regardless of whether I can make the notes happen at the right moment, I have absolutely no business playing any music that I am so disconnected from. It's disingenuous, and I'm doing a disservice to the audience by pretending that Getting The Job Done is the same thing as Making Music.
