At first I get defensive which is normal I guess, then I calm down and figure out if the criticism is warranted at all. If it is valid I ask if the critic knows how to change what I did wrong, if they give helpful advice I may very well change my behaviour. And last but by no means least I look at the source. Are they known for being critical about everything you do? Are they just plain bitter? Are they jealous? And of course don't forget some people are perfectionists and insist anything less is useless.

I hope you can find something of help from the above.

Have a great day!