The same, of course, is true for upcoming filmmakers. "This is going to be my best one yet!" you tell everybody. And it'd better be, because you've only got about one film left before everyone says "actually, yeah, you really need to get a real job." Even the greatest young film directors are going to go through the same patterns as Kevin Smith, Quentin Tarantino, etc-- there are going to be duds. This can be quite a painful thing, especially when you haven't yet made the masterpiece you're destined to make.
Take comfort in the fact that, whoever your favorite Director is, they've made bad films, apart from Billy Wilder.