The life of a movie star is often viewed as glamorous and enviable. Riches, exotic locations, fame and adoration - all that stuff is certainly nothing to sneeze at.
But at the same time, there can also be a much darker side to this lifestyle. Some actors - from child stars to seasoned veterans - can't handle pressure and will begin to veer off the rails, their money and adulation blowing up in their face.
Even putting those extreme cases to one side, actors of all levels can feel nervousness and uncertainty, or self-doubt and fear. Like everyone else, they can sometimes have confidence or esteem issues, and can occasionally be unsure that what they're doing is right.
Feelings like these have led many actors to seriously consider quitting some famous movies, from a wizarding world icon getting cold feet in the middle of the franchise, to an entire superhero team confronting their director and threatening to bail.
Of course, they ultimately didn't quit in the end, but for a moment, these stars were deadly serious about throwing in the towel...
10. Mark Ruffalo (13 Going On 30)
One of the reasons actors get paid the big bucks is because they often have to do things that are extremely uncomfortable - dangerous stunts, sex scenes, horse riding, almost getting your nipple waxed off, that sort of thing.
In Mark Ruffalo's case, that discomfort revolved around the dance scenes in his 2004 rom-com 13 Going On 30, which almost made him quit the film entirely.
According to co-star Jennifer Garner, Ruffalo felt like a bit of an idiot during the rehearsals for a dance scene set to Michael Jackson's Thriller, mainly because the people he was dancing with were far more experienced than he was.
This, understandably, wasn't a nice situation to be in, and Ruffalo contemplated dropping out as a result:
“Our first rehearsal, I think it was like Mark, Judy, and me, and Judy and I were both dancers growing up, and poor Mark didn’t know that. And he came in and he hated the rehearsal process so much he almost dropped out of the movie.”
On the plus side, it all turned out great in the end: that dance scene is one of the most memorable moments in the movie, and Ruffalo's career has been smashing it ever since.