This carefulness in the tea ceremony and other such ritualized activities was a form of discipline that allowed the practitioner to cultivate mindfulness, the Buddhist quality of being aware of what is happening at this moment.
We have seen that in Zen Buddhism, full awareness of the present moment is important, since we already have the Buddha-nature, or enlightenment, within us.
We only need to wake up to what is happening in this moment to attain enlightenment (satori).