I have learned that when it comes to criticism realizing what is and what is not actually criticism is important. Criticism is not a personal attack, and criticism does not always have to be accepted, either. As someone who has been in a ton of higher education critiques, you eventually learn (from experience, and being taught) that if you don't grow thicker skin and also understand the difference between helpful comments and, "I like this, just because," and "I don't like this," or, "this sucks, don't know why," will change your life. Everyone has different feelings about what is good and what is bad. Some people express themselves differently, may it be to lack of proper critiquing knowledge, or whatever else it may be. As long as they are trying and are not malicious, all is fair. But also, comments online can be done by anyone, and it is both a blessing and a curse. (Blessing, because you get to see what people honestly think of you and your art; curse, because some people leave comments in the middle of the night half-asleep with a power complex.)
There is a difference between bullying, off handed comments, and criticism. Criticism states what can be fixed and how to possibly fix it. Also, I feel that if it isn't really needed, or is just plain old unhelpful, it is still good to save the info for later. Artists want to improve, but not everyone's opinions on what is aesthetic matches up. That is fine. There is never a reason to be rude to someone when they weren't rude to you (not even then, but becoming defensive is not a good look for someone trying to work professionally!)
Long reply, but these are my thoughts! Thank you for the thought provoking post! I am glad you started feeling more positively about criticism. It is a huge weight off your shoulders, I am sure. ^^