There were some great responses in the comments on Monday about how you deal with critiques and feedback. I'd suggest going back and reading them if you haven't already.
As for my advice, it's pretty similar. To start, you have to know your story. What is the core of your plot? What are the character traits that are integral to your protagonist? And so on. You have to decide what is vital, so that you can know what you are willing to change (which should be a good portion of the book--this doesn't work if you decide everything you wrote is so important you can't change it). It's good to have multiple trusted CPs, so that you can look for similarities or themes in their feedback. If one person seriously can't stand a part of your book, and another loves it... that's a judgement call on your half. However, if you get multiple people telling you they really don't like something, that's when you know there's a problem that needs addressing. If you get a suggestion that is really difficult to swallow, take a day or two before you respond to it. Let it sink in, let it "simmer." Something that sounds horrible or impossible at first, might end up whipping your book into shape. You might go from thinking "I have no clue how to even fix that" to "Wait! I could do this" with a little bit of time to think it over. Also, it never hurts to try something if there is even one tiny ounce of you that wonders if it would make your manuscript better. You can always change it back.
I could say more, but again, there was already so much great advice on Monday, I think it would be too repetitive. The trick with feedback is to understand that someone is critiquing your writing, not YOU. It is not a personal attack. Someone saw enough value in your work to take the time to tell you what they think. Whether you use their suggestions or not, that is always worthy of gratitude.
If you have any more thoughts or advice about it, feel free to share!