For the longest time I thought that a drawing that couldn't be finished in one sitting wasn't worth doing. I also thought that the better you were, the less time it would take. And if you were really talented, you shouldn't have to put much effort into your work. I read an article recently that said that kids who think they do well because of their effort, not because they are talented or smart, ultimately do better in school, college, and work. Kids who believe they are smart often hit a wall when courses get hard, and their grades drop because they don't put the effort into their work. On the other hand, kids who believe they do well because of their effort will often put even more effort in when courses get hard, and their grades are maintained.
Then I realized that I am one of the former kind of student. I quit my PhD partly because classes got too hard (there were other reasons involved). I thought I just didn't know how to study math because I never had before. Now I know that I just didn't think I should have had to. The same was true for my art. I just didn't think that I should have to put a lot of effort into a drawing for it to come out well. How untrue. And with this realization coupled with the willingness to spend a long time on one drawing - weeks, at least - I am doing things I never thought possible. I made a huge jump in the quality of my art with only the desire to spend the time required to make it better.
Just food for thought.
Happy Leap Day!