E is for Edit!
Editing is a key component of writing. The key is that it has to be done.
There's also something to be said for timing. You don't want to waste your time editing while you're still creating and writing your story because....well....because it will be edited later. Often times things you've slaved over--chapters, pages, paragraphs and even sentences--will end up being edited entirely. So instead of worrying about perfecting them now, edit later once the story is complete.
When you're in the revision process, whether it's working with a critique group, beta readers, or even an editor, remember two things:
1) As an outsider they see how your story has come together and the ways in which it is presented in its best light. If pacing is off, trust them, they will know. If a character development is lacking, they're going to see right through it. As the author, we tend to be too close to our stories--and know what we've been thinking and planning--that it takes someone else's perspective to help us see what our story lacks.
2) You're the author and you do know your story best. Trust your instinct. If certain changes don't sit right with you, then they should be discussed. Maybe there's a miscommunication that can be settled through a conversation with your reader. Consider that before you take things personally. If in the end it's simply a matter of personal preference (as many times it is, as writing is a subjective business), then, once again, trust your instinct and listen to your heart. You know what's right for your story.
If you ever find that you're doubting yourself, go back and read D is for Delete and C is for Castles!