I've been painting for a few years now, but I feel like I'm only beginning to grasp the importance of this concept. I'll quote Robert Henri (1865-1929) from his book, The Art Spirit, which is packed full of such profound wisdom.
Robert Henri stresses this point:
"Insist on the beauty of form and color to be obtained from the composition of the largest masses, the four or five large masses which cover your canvas. Let these above all things have fine shapes, have fine colors. Let them be as meaningful of your subject as they possibly can be. It is wonderful how much real finish can be obtained through them, how much of gesture and modeling can be obtained through their contours, what satisfactions can be obtained from the fine measures in area, color and value. Most students and most painters in fact rush over this; they are in a hurry to get on to other matters, minor matters."
"The beauty of the larger mass is primary to and essential to the lesser mass."
"Permit no hurrying on to the lesser masses before all has been done that is possible with the larger masses"
This is such a simple concept, and yet so difficult to fully adhere to. Especially when drawing from imagination, it is tempting to skip on to the lesser details of an image. Sometimes I have to backtrack from a more detailed rendering, and re-establish the underlying form. It is so crucial to the strength of the painting.