View everything you do as an ‘interesting failure’.
I don’t mean for this to sound negative, defeatist or falsely modest; in fact I think it’s the healthiest possible attitude to have towards your work.
It is also a good way to give yourself permission to finish a project, and move on to the next thing – you will approach the new work having learned valuable lessons from your ‘mistakes’. I use terms like ‘failure’ and ‘mistakes’ in the most positive sense – trial and error is a central part of the artistic process – perhaps even the most important part, because we are always striving for originality, which necessitates journeying into unknown territory, and we are always reaching slightly beyond our grasp as we develop as artists. And we must embrace the possibility that something might not work out perfectly in order to begin the process at all…
I must confess to being a bit of a perfectionist by inclination (and I always strive to do the best work I possibly can), but at some point you must acknowledge the limitations of both your talent and of the work at hand, otherwise you’ll be tinkering forever.
A screenwriter/director I greatly admire, James Gray, said in an interview with Jeff Goldsmith for the Creative Screenwriting Magazine Podcast, that his desire as a film-maker is to ‘fail to the best of his abilities.’ I like his attitude.