Harmony - Part 1 Zhi Yi (538-597)

When entering Zen meditation the first thing which you the practitioner must do is, if you wish to enter samadhi (mental state of concentration focusing on one object) is to properly regulate the body. This must be done outside the state of meditation. Working, resting, walking, stopping, in motion or rest, whatever you do, you must in all things choose with care and discretion.

If your actions are coarse and rough, then your breath and Qi energy will follow in accord, i.e., your Qi energy will become coarse, the heart-mind will be dissipated and hard to control, and when it's time to sit in meditation you'll find it a bother; the heart will not be at peace. Because of this, even when you are outside the state of meditation, you must still use your heart-mind in a way not contrary to the "skillful means" (Upaya) of meditation.

Link here.