Know the difference between constructive and deconstructive criticism. The intent of the former is to build up, and the latter only serves to tear down. Know when and how to employ constructive criticism, and as for the other, swallow it and keep it to yourself.
The best constructive criticism is calmly delivered in the form of a reasoned question. The worst deconstructive criticism is delivered emphatically with sarcastic laughter or an angered tone.
What hangs in the balance?
Self-esteem. Relationships. Goals. Dreams.
There is how we expect to be treated, and there is how we hope to be treated. The goal is to properly merge our hope and expectations in order to receive or deliver effective feedback. Think before you speak. Ask yourself, "How would I want to be treated?"
Now, do the right thing.