To me, sadhana is a daily spiritual practice allowing time and space for an individual to turn inward.
As Yogi Bhajan (of the Kundalini yoga tradition) says, "Sadhana is self-enrichment. It is not something which is done to please somebody or to gain something. Sadhana is a personal process in which you bring out your best."
Sadhana could be taking a walk in nature, doing breath work or yoga asanas on a mat, spending time meditating or chanting, reading and reflecting on a poem, journaling or simply watching the sun rise.
Please accept this post as a possible starting point for your own practice today.
For after all, the best thing one can do when it is raining is let it rain.
— Henry Wadsworth Longfellow