Marcus Aurelius provides a more detailed explanation of how our mental patterns form our character. The key word is "frequently"—it's not the occasional thought that shapes us, but the ones we return to habitually.

Just as water carves canyons through persistent flow, our "mind will take the shape" of our recurring thoughts. If we frequently dwell on fear, our mind becomes anxious and constrained. If we regularly contemplate courage and compassion, our mind becomes resilient and kind. These repeated "impressions" literally color our "human spirit," tinting our entire perception of reality.

This quote emphasizes the power of mental discipline. It reminds us that we are, in every moment, either consciously or unconsciously sculpting our mindset through the thoughts we choose to entertain.