1. When you get your editorial letter/critique, steel your resolve, read it once, put it away, and don't think about it or act on it for at least a couple of days.
An editorial letter is kind of like a radioactive substance that you need to become gradually acclimated to over the course of several days. It needs to be absorbed in small doses and kept at arm's length and quarantined when necessary until you are able to overcome the dangerous side effects: anger, paranoia, excessive pride, delusions of grandeur, and/or homicidal tendencies. Should you find yourself experiencing any of these side effects, consult your writing support group immediately for an antidote.
It's hard to have your work critiqued, and it's tempting to take it personally. Just know that it's a normal reaction and in a couple of days you'll feel better. Once you've calmed down and are able to consider the changes without your heart racing: that's when you know you're ready to get working.
2. Go with your gut.
You don't have to take every single suggestion, and I'm often very glad when my clients don't listen to all of my suggestions and take only the best ones. If you don't agree with a change, big or small, it's okay to stick to your guns if you have a really good reason for it.
Only: make sure it's really your gut talking and not your lazy bone. Or your bull head.
And on that note...
3. Don't simply ignore the suggestions you don't agree with.
Often when someone makes a specific suggestion for a change to a certain scene or plot line you won't always agree with it and you'll throw up your hands and say there's no way you're going to make the change.
But! Even if you don't agree with the specific remedy the editor suggested, something prompted them to suggest the change, and that something could be an underlying problem that needs to be addressed, even if you don't agree with the one the editor proposed.
For instance, you may not willing to get rid of the homicidal bald eagle in your novel, even if your editor or critique partner suggests it. But surely there's something you can change to alleviate their concerns. For instance, the homicidal bald eagle may need to have a conscience.
4. Be systematic
Confronting a revision can be extremely daunting because of the Cascade Effect: when you change one plot point it necessitates two more changes so that the plot still makes sense after the change, which prompts still more changes and more and more. Ten or more changes can cascade from a single change, even a minor one.
In order to avoid Cascade Effect Terror, I find that it's helpful to work on only one change at time. Make the change, and then trace it through the book making all the necessary subsequent changes so that everything makes sense.
This way, instead of having to keep every single editorial suggestion in your head as you're moving your way sequentially through the manuscript you can be targeted and efficient with your revisions.
5. If you find yourself getting mad it's probably because your editor/critique partner is right.
Great suggestions are easy to accept: you usually smack your head and think, "Why didn't I think of that??"
Bad suggestions are easy to reject: you just think, naw, I'm not doing that.
I've found that when the suggestions make you mad, it's probably because they're right. Your brain is just having trouble admitting it.
6. Listen, listen, listen.
Easy to say. Tougher in practice.
More Nathan Bransford goodness here.