Stress
If you haven't heard, the film industry is not a low-energy, go with the flow environment. Movies often get sold before a single letter of the script has been typed. Everyone looks for the Next Big Thing, and we don't mean Brock Lesnar (although maybe we do). The only place you may see fiercer competition is in a tank full of sharks (although the sharks might be a little more polite).
This industry is not for everyone, especially not those with a low tolerance for sass, as one of the most popular outfits in the business includes sassy-pants. Rudeness, entitlement, and arrogance are just part of the game.
Don't get us wrong: a great many people you'll work with will be lovely, kind, and intelligent. And all of you will spend most parties trading horror stories about the cat-faced woman who took money up front before disappearing from a film entirely. (Yes, that happens.)
Then there's the travel. Some films may come to you, but you'll have to go to most. Don't get into this profession thinking you're going to be sitting in your underpants on your couch watching movies all day. If that's happening, you're most likely what is known in the business as unemployed.