In Writing Tidbit #2, I discussed the importance of getting feedback on your writing from others. It can be an intimidating process, one which makes writers feel extremely vulnerable. The bottom line is you should do it anyway. 
Another concern about critiques is losing one's own creative vision and "voice." If others are defining our writing for us, is the story truly ours? The issue of hijacked manuscripts is rare but legitimate. Part of the solution is finding the right kinds of beta-readers and editors. But the primary defense is knowing when to turn a deaf ear.
Yes, you do not have to do everything an editor says.
If the feedback points out a legitimate spelling or grammar error, then under almost every circumstance, the advice should be followed. If the critique is from someone knowledgeable in the specific genre or business of writing, then their advice is correct more often then not. But what if they're trying to take your writing in a new direction, one which contrasts with your vision. Consider the following recommendations that have been said to me:

• Simplify the language to make the action punchier.
• Use / don't use conjunctions.
• Shorten / lengthen your paragraphs.
• Use first-person or limited third-person perspective.
• Reveal more details about this character.

All of the above recommendations may improve your story. They might take it in a new and exciting direction. Or, they might derail your novel. Maybe the critic is just too used to a different style of author. Maybe they missed what you're trying to achieve in the tale, so the proper correction is not to follow their suggestion, but instead to tweak a different part of the story.
Being rather stubborn, I've not had a lot of troubles with ignoring a percentage of editors' advice. Other writers have told me that knowing when to disagree is a challenge. Because every example is unique, I cannot give a concise pearl of wisdom in this matter, but I can suggest three questions to ask yourself when sifting out misguided advice:

1. Am I being humble enough to accept change?
2. Am I fighting over this point for a significant reason?
3. Is this incorrect suggestion hinting at a needed change somewhere else?

One more thing: A lot of bad advice is the result of preferences being repeated ad nauseum to the point of becoming a "rule." Jeff Gerke's The Irresistible Novel delves into a lot of these and explains when and when not to follow them.

In honor of all those crazy folks doing National Novel Writing Month, I present The NaNoWriMo Family Takes a Road Trip

Dad: Check out the odometer. Another 5,000 words down-
Mom: LOOK OUT!
Dad: What?
Mom: You just hit a typo.
Dad: (silence)
Mom: Should we go back to help it out?
Dad: There's no time.
Mom: But what if we don't see it on the way back-
Dad: THERE'S NO TIME!
klunk-klunk
Mom: Would you PLEASE pay attention. You hit another one.
klunk-KLUNK
Mom: And now you've hit a grammatical mistake! Just pull over to let me drive.
Dad: No, I've got this.
Mom: At least pull over so we can use the restroom.
Dad: There's no time! Here. Use this soda bottle.
Mom: Well, would you at least hand me the map so I can plot our course?
Dad: Plotting? We'll never get there if we do that.
Kid: Are we there yet?
Dad: No! We have 35,000 more words to go, and if you keep asking, I will turn us around at the next paragraph.
Mom: Watch out ahead. Cops like to sit at this word sprint.
Kid: Susie said her mom only has 20,000 more words left.
Dad: Well, hurrah for Susie's mom. Some of us actually type words that are longer than two syllables long.
Kid: Susie said her mom's book is better than yours.
Dad: Well, you can tell Susie that now she's dying in chapter 16.