From ‘The Yellow Emperor’s Classic of Medicine’ translated by Maoshing Ni

“During the winter months all things in nature wither, hide, return home, and enter a resting period, just as lakes and rivers freeze and snow falls. This is a time when yin dominates yang. Therefore one should refrain from overusing the yang energy. Retire early and get up with the sunrise, which is later in winter. Desires and mental activity should be kept quiet and subdued. Sexual desires especially should be contained, as if keeping a happy secret. Stay warm, avoid cold, and keep the pores closed. Avoid sweating. The philosophy of the winter season is one of conservation and storage.

(…)

So the full cycle can be seen. Spring is the beginning of things, when the energy should be kept open and fluid; summer opens up further into an exchange or communication between internal and external energies; in the fall it is important to conserve; finally, the winter is dominated by the storage of energy.

(…)

The transformation of yin and yang in the four seasons is the basis of the growth and the destruction of life. The sages were able to cultivate the yang energy in spring and summer and conserve the yin energy in autumn and winter. By following the universal order, growth can occur naturally. If this natural order is disregarded, the root of one’s life will be damaged and one’s true energy will wane.”

Still regarding the winter season, read this interesting article by Roni Edlund from Lotus Nei Gong International, on the Scholar Sage website, the online magazine of the school:

http://www.scholarsage.com/winter-the-forgotten-season-of-modern-society/?fbclid=IwAR044JdvvP9-wCE7dQdZg9e19QZRUqrjBs3BKFr5dv1l408Yvr2SbuRUUps