Seek Serenity in Activity
Tai Chi uses serenity in combination with activity. Even when you are moving, you remain tranquil. When practicing the postures, the slower you move, the better the result.
Slowness enables your breath to become deep and long with the chi sinking to the Dan Tien. This will naturally prevent the pulse rate from elevating.
It is important to practice the movements slowly, so that you can understand the meaning within the movements. Practicing slowly helps to regulate your breathing enabling your breath to become deep and long allowing your chi to sink to the Dan Tian.
Practicing in this manner also prevents the fault of top heaviness which is caused by the Qi rising up. Serenity can be sought in any activity in life.
-The Tai Chi Classics