When you create anything, expect negativity. You will encounter it. There are just some people who cannot be supportive or positive if their life depended on it.
I just encountered one that took me deep into depression for one night.
I had someone I knew review a children's book of mine. She wrote about 2 pages of problems with it. Most of the 'problems' were her opinion on how a sentence could be worded better. There was not one single positive thing said in any of it. What did that say to me? That I did nothing right.
Now, that doesn't mean this person really thought that but that is the message that came across. I about threw in the towel when it comes to writing. Thank goodness for a friend who threatened to kick my butt.
If you read over someone's work, try to point out the positives. If you are the one receiving the negative, take it with a grain of salt. There is always something to pull from the list of negatives to help your writings but don't let the negative words stop you from pursuing a dream.