Productive with Art

I am an artist. I have educated myself on the skills necessary, I practice a whole lot, and I believe I am capable of much but haven’t yet tapped in to my real potential because I am in my own way. When I sit down to create, I often don’t get far with the pieces of art and don’t create much content, because, to me, pieces often do not turn out like I envision and like I could reasonably expect. Also, it takes me way too long to finish whatever I do work on.

I am doing my thought work to determine the thoughts going on that are hindering me from being productive. I begin by asking if I am afraid of what others will think. Maybe. Maybe I’m afraid of being judged. But I’m also wondering if it because I don’t want to hear the negative feedback and judgment from my own brain.

Will you please help me try to get to the real issue so that I can do my art with freedom and be very productive?
What thoughts do I keep in mind while creating my art?
Also, please help me to assess my work accurately. How do I really know if it’s B- work, that it’s really good enough to move on to the next piece?

I thank you very much for your help.