That can be interpreted in a simple manner even though emotionally speaking, it's hard to accept. The main reason for your discouragement is that your standard of art is dependent upon other's people opinions. Sure, in terms of business, we have to know what they like and dislike to shape the story of our art. That's one way of having a feedback. But that kind of art is not just any simple art. I like to call it "commercial" art for obvious reason. That art was made to be sold. It's for business. Being attentive to what the readers or customers say is a good skill to have. But, those opinions tend to be "subtractive" rather than "additive" (which I will explain later using sculpting as a metaphor).
Commercial art is made for others. They might like your drawing of a portrait but to you is 1000 times boring due to, say, its repetitive nature. It becomes boring. Such intention of art limits you to go outside the box. You fear of what they are going to say if the new things you do horrify them. Possibly it could breer hate. And you're correct to have such view. Every exploration tends to have tons of mistakes. That's to be expected. That's what it means to lear. Even Albert Einstein confessed it himself. But if you won't explore, you will just be repeating the same "feeling" you get there: restlessness and anxiety.
You could abandon it altogether and move on different department. That's sure to make you forget it. But of course, that's too extreme. It's not essential. The trick is actually deceptively simple. Know the "room" or objective of your arts. If one room is for the commercial art, then the different room must be far away from it. You can call that distant room as personal art because it's just all about you. By exploring yourself, you can know further of who you are in the same way of knowing what else you can do potentially. This explorative art is really just an experimental art. You experiment with new things, and see if this new discovery could be of use to an existing paradigm. Experimental art because it does use your capacity to predict what would happen if a technique is done. It's a scientific endeavor but not a symolic one. It is of intuition. It's primarily used to add a skill path in your mind.
Now, if you become comfortable of doing art just for the sake of doing it, you will realize that in "that" room, art itself is the reward, not the opinions of others. Truth doesn't concern of what people have to say. It's just objective. And art done for the sake of art, just as playing game for the sake of game, is the primary motivation you might want to learn.It can be rewarding in itself. You add new knowledge. And that thing is actually essential before you do some "carving."
As for the subtractive, I said I would use sculpting as a metaphor. I do think it's a good metaphor which you will see now. In commercial art, you take criticism to shape your art which is to be sold. That is like sculpting, specifically carving. If you have a big clay and you want a man to be revealed inside of it, you have to carve the excess away. You subtract what is not needed. And in a similar fashion, you also do that in your commercial. When an idea or image or story scene does not work well on the readers, you remove it away. That is how you want to reveal the inner beauty of your masterpiece. However, if the clay is just like a small marble while you have a large carving tools, I am afraid you can't reveal the man inside. The clay is too few to make a figure. Likewise, if you have reduce or subtract your ideas too much, then you become a very limited creative fellow. It's not even appropriate to call one a creative if the person is stuck on a small island. If you let the opinions of others "subtract" your potentials of learning new things, then you are doing commercial art wrong. You first make art just for yourself or for art's sake before you offer it to others. Enjoy it yourself first before you let others enjoy it too. There are proper orders to reach a goal.
In conclusion: shift your mind elsewhere so that you can explore new experiences or techniques. Most of our understanding comes from experience and without experiences, ideas are mostly dry. So, just add tons of new experiences by trying different things all while expecting something really different. This is hard at first but by expecting nothing, you can get something.
ps: I apologize in advance if the text is kind of cold and offensive for a person having deep emotional burdens. If ever it was offensive. But I want you to try look at them in a bit of a more practical manner than mere motivational uplift.