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, or simply watching the sun rise.
Please accept this post as a possible starting point for your own practice today.
"Luke," from Dog Songs by Mary Oliver
I had a dog who loved flowers. Briskly she went through the fields,
yet paused for the honeysuckle or the rose, her dark head
and her wet nose touching the face of every one
with its petals of silk, with its fragrance rising
into the air where the bees, their bodies heavy with pollen,
hovered— and easily she adored every blossom,
not in the serious, careful way that we choose this blossom or that blossom—
the way we praise or don’t praise— the way we love or don’t love— but the way
we long to be— that happy in the heaven of earth— that wild, that loving.