Rewriting is horrible. Sometimes an editor doesn't brief the writer clearly, other times the writer doesn't read the brief properly, other times the piece just doesn't work as originally planned.
Whatever the reason, it is horrible, but sometimes rewriting has to be done. And I think there are two golden rules for the humble writer as s/he sits there gloomily contemplating a few hours of extra work.
1. Be Nice
Don't criticise the editor, even if they have made loads of mistakes. No need to be a doormat - in fact, being a doormat is a VERY bad idea. But just remember that however difficult the editor is, they're usually not being awful just for the sake of it.
Editors are trying to create a good magazine to a deadline. They often have a higher-up editor or a publisher or someone else putting pressure on them. They're human. They want to work with people that do the job without fuss. And they have the power to hire or fire you.
2. Do Check
Find out what's required now. If you're not sure what you did wrong - double check and be sure you understand this time round. Make sure your copy is in on time, and that it is as good as you can make it. If you don't have time to do all this, then make time.
Which all sounds very good and very professional, and it is. But I have to add that occasionally - just occasionally - difficult editors ARE just too awful.
Just Too Awful
Perhaps the worst I ever had was a man who was new in the job and so anxious about it that he wanted no less than six rewrites of a long, long story. I was sorry for him, but my sympathy wore ever thinner each time he changed his mind at the sight of the latest rewrite.
The story in the end was a mess, because in the end I had no idea what I was supposed to be doing, and nor did he. It was published, and I wasn't happy with it. I don't know if he was, but I didn't work for him again.
But then, I didn't need to., hehehe! That's the joy of being part time.