You get to contribute so significantly in the editing room because you shape the movie and the performances," she says. "You help the director bring all the hard work of those who made the film to fruition. You give their work rhythm and pace and sometimes adjust the structure to make the film work ‑- to make it start to flow up there on the screen. And then it's very rewarding after a year's work to see people react to what you've done in the theater."
Thelma Schoonmaker on Wikipedia