Walt Whitman uses a beautiful natural metaphor to illustrate a principle of mental focus. The "sunshine" represents hope, opportunity, and the positive aspects of life. The "shadows" symbolize problems, doubts, and past troubles.

The instruction is simple: consciously and deliberately orient your gaze—your attention and energy—toward the light. By maintaining a forward-looking focus on what is good and what is possible, you naturally relegate the negative "shadows" to your past. They don't disappear, but they lose their power to darken your path.

This quote is a prescription for cultivating optimism. It doesn't deny the existence of shadows, but it provides the strategy for overcoming them: a relentless and intentional positivity that keeps you moving toward the light.