Critique groups are for one purpose: To nudge and prod you into writing the best story you are capable of writing. They are your friends. If you manage to get into a good one, with really good prodders, it might hurt a little at first. But, when you’ve rewritten that line, phrase, or paragraph that you thought was perfect and now find it to be more perfect, the pain turns into glee.
Once you’ve become too close to your story to see its flaws, your critique friends will see things that you have begun to skip over, especially after reading that same line for the hundredth, maybe thousandth time. It is nice to have a group of five or six individuals that can look at your work from different angles. One person might be tuned in to all the typos and grammar problems, another might see plot issues, and yet another might be sensitive to repeat words or too many compound sentences.
I love my circle of critiquing buddies, and always look forward to my piece returned to me with marks all over it. I know they have read it carefully and are offering their sincere suggestions.