I talk to my students about their grades using this Rubric Chart. I tell them that they can know their work is good in art by checking their work against the Criteria Chart that goes with each art project along with what is listed here which applies to all work: creative (your own ideas) neat, clean work, craftsmanship, name and teacher code on work, etc.
Criteria Chart (not shown)
We go through what a Criteria Chart is. Each project has it's own criteria chart. They create one for what a drawing should look like. Then I show them a drawing I've done and they give me a grade. They really get what a Criteria Chart is by grading me.
I'll Try vs. I Can't
How can they make their work better? One way is to have a positive attitude and say, "I'll try." But, also by listening, following directions and the Art Room rules.