Well, simply put, don't take it personally. A lot of people want criticism, but then they feel as if the person criticizing is nit-picking. You can't take it personally. They're just there to tell you what to improve and what's fine.
For example, I like writing. I have people read over my stories. I trust these people to give me both good and negative feedback, because you can always improve, and I know that when they mention something, they are my friend and are just trying to help.
Getting it from a stranger would be a little worse, but unless they have a grudge or seek vengeance, don't worry about it. Focus on what they said they should do, and ask them for advice. How to improve what was wrong, etc. Often your weakest area is their best.