Tai chi both affects and is affected by our emotional state. Emotions engage the whole body, including the neurological, muscular, and endocrine system, and tai chi does as well.
Any form of meditation can calm and regulate the nervous system, but emotions exist in all the tissues of the body. They are stored long-term as chronic tension in the muscles. The active relaxation and relaxed action of tai chi practice slowly dissolve and release emotional issues from within.
Emotions that come up during tai chi practice are a positive sign. Tears, laughter, body heat, are all signs of emotional charge being released from the body, and should be welcome signs of progress. The important thing is to hold to your center, maintain your composure, and allow the emotion to flow out of you unhindered, rather than sweep your awareness along with it.
Any time you are feeling emotional is a good time to practice. If you are feeling too emotional to practice, that is the best time. You don’t have to wait for emotions to get trapped in your body before you process them, you can use your practice to process them actively while they are happening.