Deal with the Reality on the Canvas
The Art professors in school were always "out there" so to speak. They were always talking cryptically about various art concepts and ideologies. Sometimes you wondered how they got to that borderline crazy, magical place in the first place. Nevertheless, they always imparted valuable knowledge that may have not been applicable to you personally at the time but somehow made sense further into your art future, and then you think you discovered it yourself from some divine inspiration! :D
All of my art professors were awesome in one way or another. My college Drawing II professor had a profound effect on me. He would get really miffed if you drew any kind of "S" curve or if you signed your name on the art itself. I still wrestle with the "to sign or not to sign" dilemma today! XD
During one of the night classes I was working on a fairly large abstract pencil drawing, and I was kind of stalled on where to go next for the unfinished work. The professor noticed my vacillation and approached me. The next words that came out of his mouth still resonate with me to this day.
"Deal with the reality on the canvas, not the image in your head."
It sort of made sense at the time, but it felt more like the artistic equivalent of a zen koan. After that night I forgot about that little nugget of wisdom. Too bad. Those thirteen words were instrumental for me to learn to loosen up so to speak many years later.
My takeaway from that brief moment in time was that we, as artists, have a mental image in mind before and during the creation of a work, and that we are in a constant struggle to replicate that image exactly onto the target medium. Essentially, this may set you up for failure from the beginning since you may inhibit your innate expression and mark making inclinations. Maybe another way to look at this is to just roll with the "artistic happy accidents" which was a frequently heard phrase from one of my highschool professors.