Some kinds of trees make themselves quiet in ways we can see: We say that they ‘sleep.’ At night, they fold up their leaves. If you go lie under them, you’ll have a clear view of the stars in the nighttime sky. But when day comes, they’ll spread out their leaves and give a dense shade. This is a good lesson for the mind: When you sit in meditation, close only your eyes. Keep your mind bright and alert, like a tree that closes its leaves and thus doesn’t obstruct our view of the stars.
(Ajahn Lee)