As far as I know, there is no known credo about the masochism of being a ballerina. But maybe after Darren Aronofsky's Black Swan, there is a chance of such a phrase being coined. Gradually weaving in elements of the surreal and sinister, the style Aronofsky became esteemed for with Requiem for a Dream is ever-present and ideal for this particular narrative, the story of which was conceived and written by Andres Heinz (one of the few working screenwriters able to prove that going to film school isn't a total waste of time and parentally funneled money), with help from Mark Heyman (writer of The Wrestler, also directed by Aronofsky) and John J. McLaughlin.
While I'm sure your primary interest is in the miasmic lesbian sex scene between Natalie Portman and Mila Kunis, I'm almost positive you'd rather see it for yourself than hear me describe it in writing. For blokes especially, it is something that requires bearing actual witness. Suffice it to say, there is no nudity in spite of the scene lasting for several minutes. The physical exchange has audiences and censors alike abuzz with shock and awe over the MPAA's arbitrary rating system. In fact, another upcoming film, Blue Valentine (starring Ryan Gosling and Michelle Williams), was slapped with an NC-17 rating for a similar instance of oral sex, as opposed to the tame R rating that was given to Black Swan.
The other notable aspect--though some might disagree--of Black Swan is the rare appearance of Winona Ryder as Beth, an aged ballerina who is pushed out of her residency by the director of the ballet, Thomas Leroy (played by the oddly attractive Frenchman, Vincent Cassel). It seems that, only recently (with Star Trek), Ryder has been typecast into roles that fall into "the older woman" category. She may be 39, but she looks almost exactly the same as she did in her Edward Scissorhands days. And, not to be totally unreasonable, but she looks pretty much the same age as Natalie Portman. The way to gauge if an actress is over the hill by Hollywood standards is if you have to put makeup on her to give the illusion of an older appearance. They may not have done this in Black Swan, but they more than definitely did in Star Trek.
And, speaking of older broads, Barbara Hershey, who hasn't really had a major film role since 1996's The Portrait of a Lady, also shines as Nina's (Portman) psychotic mother. More than likely a contributing factor to Nina's demented metamorphosis into the Black Swan, Erica is the primary source to arresting Nina's development (excluding the fact that she lives at home. I would endure living with my mother too if it meant having an apartment on the Upper West Side). Not only does Nina still have all of her childhood relics, stuffed animals included, she also can't even leave the apartment without the third degree (a detail that Lily, Mila Kunis' character, overtly belittles when she comes to visit Nina one night).
In conjunction with her mother's sinister nature and foisted pressures, Nina allows the dual role of White Swan/Black Swan to consume her, both physically and emotionally. This is, I suppose, the reason she starts to hallucinate visions of her alter ego wherever she goes (on the subway, in the mirror, in the bathtub, wherever really).
The mind fuck is only intensified by Nina constantly confusing her alter ego with Lily (allegedly, their torrid night of lesbian love was all in Nina's mind). Her fragile state isn't helped by a subway ride that involves a disgusting old man (is there any other kind?) who masturbates to her because they happen to be alone together in the train car (the unfortunate thing is that it's not even an embellishment. Way weirder shit occurs on the New York City transportation system). So paranoid and frustrated by her increasing aberrations, Nina even goes to visit Beth in the hospital to tell her that she finally understands what it feels like to have someone try to take something away, specifically the part in Swan Lake. Beth only responds by grabbing her arm abruptly, transforming into the Black Swan version of Nina, and then stabbing herself repeatedly in the face with a nail file. Yeah, it's definitely one of the more disturbing scenes in the film.
What Heinz's script, paired with Aronofsky's baleful directorial techniques, eventually hits you over the head with is that a person, expressly a dancer of the ballerina persuasion, must suffer for her art--even if it means embodying an almost satanic being to do so.