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.
I Stretch My Arms, by James Harpur
I stretch my arms like a swan flying And watch, weightless, the world turning So high up I can see – endlessly it seems Rome and white mountains rising beyond, Triremes at anchor in still Alexandria Pearl-divers practising from rocks The wind wandering through the wilderness. The sun casts no shadow of the compass. I am rooted to the spot, rotting inside I had no choice but to choose this perch And now I cannot choose any more Each choice I made was like a nail Fixing my arms to embrace the world.