Gotta have opposites, light and dark and dark and light, in painting.

This reflects a common teaching point in painting instruction: using contrast (value and color) to create form, depth, and visual interest. It aligns with the kind of guidance often given in beginner-friendly landscape painting demonstrations.

The idea is that a picture feels more believable and engaging when it includes contrasting elements; highlights stand out because shadows exist, and dark areas gain meaning because lighter areas are nearby.