I want to harmonize with Mother Nature!

Bill painted what he saw in Mother Nature. Bill knows how light would affect this scene, so he applies it to his painting. Your painting must make sense. How you do that is up to you. In this case, Bill uses his fan brush and adds highlights to the edge of the rock where the light would hit. He could have put a bush there or just highlighted the rock. Take your lead from Bill. You are the almighty creator! You are the leader of light!