"When you follow wandering thoughts,
you are restricting your awareness;
your mind is restricted to that particular thought train.
When you don't follow your wandering thoughts, your mind is free and open. Tell your mind it can go anywhere it pleases, but you will not follow it. At this time your body will be relaxed and your mind will be free because you are not restricting it in any way. This is the most enjoyable time. You have nothing to do. Both mind and body are at ease.
[...] With meditation you can reach a point where there is no fluctuation, no scatteredness, no confusion. You reach a state of equanimity. Your mind is peaceful. There are no waves. That is being clear. In that situation, however, there are still thoughts. But if you maintain that clarity, you won't think about them." - Ch'An Master Sheng-Yen (Zen Wisdom)