You can't always get what you want.
The Rolling Stones, obviously, were philosophers.
When you're faced with the real world, there simply are going to be times when you can't always get what you want. We want so many things, and often those things that we want conflict. This is a basic truism. Some desires will come in conflict with others.
In decision-making contexts like design, it's common to talk about trade-offs, two (or more) values that conflict. Howling Wolf has a song in which he says "I'm built for comfort; I'm not built for speed," using an automotive metaphor apt for this discussion: many features that increase automotive comfort increase the car's weight, thus reducing the car's speed (all other things being equal; obviously one could use a more powerful motor to offset the increased weight while maintaining the same speed).
In economics a related concept is the concept of opportunity cost. The cost of choosing one course of action is the opportunity to pursue a different course of action. If we invest some money in stocks, we can't invest the same money in gold, too. As the saying goes, "you can't have your cake and eat it, too." (Which, incidentally, I've always understood to mean, approximately, that there are trade-offs or opportunity costs, that there are some decisions that exclude others. But, while I've understood it that way, I've also always wondered about it, because, you know, if you have a cake, what else are you supposed to do with it but eat it? And if you don't eat it, it goes bad, right? I mean unless it was made by some bakery like Hostess, that carefully prepares their cakes for long shelf-life. I suppose even Twinkies go bad eventually; or at least go worse, because I wouldn't eat a Twinkie fresh from the factory.)
In any event, the writer would do well to embrace the concepts of trade-offs and opportunity cost. While it is a sad thing to give up a childish fantasy that you can have everything you want, you're more likely to find real happiness, as a writer, and in your life, if you can recognize that you can't always have what you want.
If you can approach your work from a place where you're seeking not perfection, but a successful relationship with your reader, or a successful resolution of a specific method of presentation, or some other limited goal, then you can finish and submit the work to someone else. And that is the main goal--that is what separates the writers from the people who sit in their rooms, with their pads or notebooks or computers, writing but never sharing.
The relationship between perfectionism and procrastination can be resolved from this place. It is not that one is sacrificing one's moral strength or sacrificing one's integrity to produce a work that fails to resolve all questions and all problems, rather it is a sign of moral strength and integrity to accept both the limitations and possibilities of life and still to attempt to produce work to share with others. I'm not suggesting that one should not strive for the best, but rather that one recognize how trade-offs and opportunity costs affect our lives and circumscribe our efforts.
Of course, one should always strive for the best. And why not always looks for win-win solutions? The fact that there are trade-offs does not logically imply the need to hurt another for one's own gain. But perfectionism can be paralyzing if it cannot let us get beyond the fact that there will be trade-offs.
Perhaps the most crucial resource for writers who are stuck is to focus on the time we have. We can always trade more time for more quality: if we spend more time writing, we can (almost always) improve on our effort. But what do we give up for that trade? We give up everything else that we could have accomplished with that time. Do not try to create perfection; it's an endless treadmill. Instead try to create something that satisfies both you and the readers that you hope to reach. Ultimately, we write to be read, don't we?