How to use a joyful mind

Before taking students on a hike during a winter retreat, Sifu asked her students to each hug a tree and tell the tree, "I'm very happy!" The students were a bit shocked by this instruction, but eventually each hugged a tree and said, "I'm very happy!" Sifu explained that this joy is very important to the practice. Then she asked...

Sifu: Now that you have this joy. What do you do with it?
Student 1: Keep walking (on the hike)!
Sifu: Only that? Keep walking is not bad, but it is not enough. We must return this happiness to each step that we take and offer it to the the ground, the universe, and all beings. This is the correct function of our happiness.

Zen Master Seung Sahn always taught us, "When you are not thinking, you and the universe become one. You are the universe and the universe is you. You and the universe are never separated." If you are not attached to the words "happy" or "joy", and only become one with the tree, then you and the tree are one. No subject, no object. There is no "I".  Inside, outside become one. At that very moment, you only have gratitude. The tree only gives unconditionally. Whenever our mind returns to this unconditional love, we do not need joy, we are the joy. Because this mind only wants to give and be filled with gratitude.