I think obsession is an important quality to have when it comes time to rewrite. But you also have to know when to turn the obsession off and move on.... If you find a script is laughing at you, I tend to throw it in the corner of the room for a while, to laugh silently at me, until I can work out how to fix the darned thing.
Frustration can be a part of the rewrite process too, it usually means I've missed something really basic - like an aspect of character. Which tends to reveal flaws within my own character.... Oh joy! Isn't the writing process fun! Self-discovery: AARGH! ;)
Stamina is another important quality to have, I'm finding out more about mine all the time. Sticktoitivity is my other word for it. ;) Bums on seats. Get typing! Get it done! ... ... I bought a fridge magnet last year: "The lift to success is broken please use the stairs." - a useful reminder that writing is not a 'get rich quick' scheme, no matter how much you want it to be.*
Plenty of other writers, better than I, have covered Rewrite on their blogs and websites. ... And I'm sure I shall write more on the subject in the future, which is why I have called this part 1.
But right now I'm procrastinating when I'm supposed to be writing (amongst other things)... so, as I said in the previous post, I'd better get on with it!
*NB: I don't write because I want to get rich. I write because I NEED to write. If that should happen to lead to a career that actually pays enough money to live on, that would be a spectacular bonus. But it's not my primary driver.