You take it one step at a time and the basic rule is to work on movies you would like to go see because it takes too long and it's too hard to work on a project for somebody else just because it's a job. When it's four in the morning and you've been working 18 hours a day for 10 months straight you had better care about the film, otherwise you couldn't put out the way you have to. To do it well, you don't have any other life, so it better be something you enjoy.