Here are a few tips for understanding and dealing with Seasonal Affective Disorder (SAD), as the daylight is less until the solstice.

Make a point of exposure to sunlight each day, even if hazy or rainy, and looking upward.

Practice Anuloma Viloma or alternate nostril breathing.

Practice Trataka or ghee lamp gazing for increasing photons reaching the pupil and optic nerve.

Meditate on light at the third eye, and feelings of darkness reduce.  Soon light returns.