Being around creative people of all different stripes provokes observations, especially as you see different people making the same mistakes.
One thing I see a lot: It is very difficult for creative people to turn their back on something they've already spent time on. They're worried that if they quit now, all the hard work they've poured into $PROJECT will evaporate like so much morning dew in a blast furnace. (See the "sunk cost fallacy" for more on this.)
I run into this constantly, and I'm constantly surprised by two things. One is how each incarnation of it is as distinct as the person, and the creation, in question. No two people seem to incarnate this dilemma in the same way. Some of them put a project down and pick it back up again; some of them just ram themselves head-first into it over and over. Mostly this takes the form of rewriting the same project over and over and never making any real progress on it — because it was conceived at a time where they occupied a very different mental space from where they are now, and so it's near-impossible for them to do any real justice to it. But the net result is the same: they're stuck.
Thing #2 (no, not of the Dr. Seuss variety) is how whenever the people in question have this behavior pointed out to them, they respond with shock, denial, and even a certain degree of outrage. They don't realize they're being this stubborn, and when they do, they get angry because they feel like someone is telling them to give up and get a life, when the real message is for them to stop pouring all their energy into the toilet.
I've seen some people really mess up their creative lives by getting mired down in the rut of sunk-cost thinking, because the biggest damage it can do to them is internal, and not always readily visible to themselves or others. Resentment, for instance: a person who clings against all odds to a project they stand little chance of finishing is only going to feel all the more sullen when they see others around them pass them by, because they weren't miring themselves down.
One of the many differences between an amateur and a professional is how they deal with their ideas. An amateur clings to every idea that comes across as if it were his last one ever, a sign they don't yet have faith in their ability to devise and discern creative ideas. A pro knows full well that it isn't about the idea but the expression of same, and has faith in his ability to find a new idea when the old one doesn't work out ... in part because he also knows his interest in a given idea may well only be a product of his own very mutable moment in time.