Honesty, the first thing you have to learn is the difference between constructive criticism and destructive (or abusive) criticism. It is important to clarify whether the criticism is meant to bring improvement or to cripple you.
It's very easy to tell which is which.
A constructive criticism would look like a normal debate message, and destructive types are generally full of insults without much arguments about the topic. You don't need a PhD in pshycology to figure that out.