Stop squirming. I know you're scared, I was scared too. The one simple rule about taking a critique is - TAKE IT. Don't interrupt, don't disagree, don't attack or get mad or withdraw, and under no circumstances climb under the bed (for all you know, your childhood monster might be waiting there to snack on your feet). Now that you've written a short story or finished a manuscript, sent it off to friends and got your first critique, it might be a dip into a harsh reality for you. The reason? You're emotionally attached to your story, your critiquer is not. Here is how to deal with it:
Listen. I mean it in the simplest sense of the word - listen. JUST listen. It doesn't matter how you decide to send your material to a critiquer - via e-mail, on Twitter as a link, or mention it in the middle of a chat at the bus stop (yes, use every opportunity you can to ask others what they think of your work). No matter the method, make sure you put your personal hurt aside and really listen to what the person is saying. What did they like? What did they not like? On what page did they put the story down? Would they buy it if it was for sale? What can you do better? Those are the questions you might want to ask (AFTER the critiquer is done talking).
Thank people for their time. It's no small feat for someone to set aside time to read your material. They could've opted for a published classic that's been professionally edited a thousand times, yet they chose your work, riddled with little mistakes, "oops" moments, continuity issues, you name it. So thank them profusely, even if it's a simple "Thank you for your time." EVEN if they tell you they hated it. There are never too many times you can thank somebody.
Apply the 80-20 rule. Now, to the fun part. Guess what - DON'T apply most of the criticism you get, you can't please EVERY reader. Instead, use the 80-20 rule, meaning, if 8 out of 10 people told you the same thing, change it. The rest - throw away. Here is where you have to remember the LISTEN rule - different people might be telling you the same thing differently. If you really listen, you will know what I mean. As an example, my boyfriend told me to cut out a scene because it was redundant, but I was so in love with it, I didn't listen. Then my son didn't say anything, but stopped reading on page 32. Guess where that was - yes, same scene. He got bored. I cut it.
Trust your gut. Your gut will know when the critique is wrong and when it's right. Your gut will get that funny "I-thought-so" feeling when it knows you need to make a change. In fact, you probably knew about it all along but decided not to deal with it yet. Whatever the reason, after you get those 8 people tell you the same thing, before you apply it, search your emotions. Does it feel right? Don't cheat. I remember how I knew all along that the scene mentioned above was a filler, but I was so in love with the concept, I wouldn't let it go. Until I did, and I'm glad I did - it reads much better now.
Critque others. You can't possibly understand how to apply a critiue to your writing until you've critiqued someone else's work. Number one, it will teach you what mistakes NOT to make. Number two, it's all about giving. You give, they will give back The cycle will repeat. Number three, you will see how the other person responds and experience first hand what it feels like to be yelled at, or, in mild cases, simply ignored. Try to remember that when the tables are turned - it will help you be graceful.
To summarize, get over the idea that your writing is perfect. It is not. There is always room to improve. At the same time, don't beat yourself up constantly - that doesn't help either. Instead, go cry on the shoulder of a dear friend, blow your nose, then get back to work. Remember, everyone loves an underdog. Be humble - and people will help. It takes a village...