The Plateau of Self-Improvement

Is there such thing as chess skill self-improvement? If there is, what are the most effective ways of it? Books? Software? Playing on and on and on? A comprehensive study plan? Is self actually ever able to help self by following a program? Or, you are facing the dilemma of one hand clapping? Is it akin Baron Munchausen escaping from a swamp by pulling himself up by his own hair? Where is the plateau, what is the self-limiting factor?