Sadhana is a general reference to the active pursuit of a Yogic tradition or Yogic lifestyle that aims at progressing to a spiritual goal. It’s a term typically used in Asian spiritual disciplines in Hindu, Buddhist, Jain, and Sikh traditions.
Traditionally, Sadhana is done daily with the goal of achieving worldly detachment and spiritual perfection i.e. spiritual liberation or Enlightenment. The person who follows (or does) Sadhana is called a Sadhu (the female form is Sadhvi), Sadhaka, or Yogi.
Doing Sadhana usually means that one follows a certain type or style of Yoga, such as Ashtanga Yoga (Sutras of Patanjali), Karma Koga, Bhakti Yoga, or Jnana Yoga, and so on, including carrying out the instructions and/or activities that belong to the practice.
Sadhana can include the use or application of Mantras, meditation, Japas, Pujas, Asanas, and/or Bandhas, among other Yogic techniques. Nevertheless, everything can be one’s Sadhana: the way one talks, walks, or eats, the way one sits, stands, or breathes, the way one handles emotions and thoughts, and so on.
In a more general sense, one’s Sadhana can also be seen as adhering to or following a certain spiritual state of mind, approach, or attitude.