Success in any field requires a measure of understanding that things change, things grow and things die. And that you have to let them go. And that the ideas that you have about your career may not necessarily be the ones that are the best for you or the ones that are supposed to happen or the ones that are truly what you want.
And also on Big Ideas, 'A successful TV writer on why not to go into TV writing'. The kind of sobering realism you either learn to hate or ignore if you're going to keep writing. What kind of writer hasn't already developed a 'fuck you' attitude anyhow, eh?