For a human being, the mind is the most important element. A meditator must make special efforts to safeguard and purify his mind. Most of us tend to misconceive and be confused about the relationship between the mind and its objects.

How do we misconceive? For example, there is a sound – that is just the object of the hearing consciousness. Misunderstanding happens when the sound or the object of hearing no longer exists – disappears, but our mind continues to hold on to it. The same thing happens with colors. When colors come to the eyes, we see colors. However, when the colors are gone, our mind still clings to and refuses to let go of them. This is why we always feel sad. Why? Because objects have vanished, colors have disappeared, and sounds have gone, but our mind still grieves and laments over their disappearance.

Meditation Master Khippapañño
From: Experiencing The Dhamma