From Lao tzus text. The Tao te ching.

Empty your mind of all thoughts. Let your heart be at peace. Watch the turmoil of beings, but contemplate their return.

Each separate being in the universe returns to the common source. Returning to the source is serenity.

If you don't realize the source, you stumble in confusion and sorrow. When you realize where you come from, you naturally become tolerant, disinterested, amused, kindhearted as a grandfather dignified as a king. Immersed in the wonder of the Tao, you can deal with whatever life brings you, and when death comes, you are ready.