The first job I was offered was as an editorial assistant. I think it was the best thing for me, in terms of being a storyteller by nature, to have spent years being an editor because I learned so much from it. ↗
As for collaboration - I have done a lot, 26 books, and found publishers increasingly resistive to them. It's not that the books are bad; editors won't even read them. ↗
And if you want to know why great editors scare the pants off of writers everywhere, read 'Eats, Shoots and Leaves' by Lynne Truss. The punctuation police are everywhere! ↗
And in Hollywood, you know, everyone is an expert. Most of them are expert editors. They can't direct, they can't write, they can't act, but, by God, they all think they can edit. ↗
Successful model? That's a myth. The year I modeled was the most painful year of my life. Editors would always talk to you in the third person as though you were merely a piece of merchandise. ↗
Rewriting is a large part of the whole job. And get rid of stuff that's not working. Just pare it down until it's a beautiful thing you can hand in, probably late, to your editor. ↗