What is sādhanā ?

The word sādhanā comes from the word sādhya, which means “to achieve” or “to aim or focus”. Any intense practice that is done with 100% focus is called sādhanā.
Sādhanā is a long path. To do sādhanā, one requires great patience. sādhanā can be done in any subject, be it music, yoga, archery or any other practical art. The goal of sādhanā is to become one with the subject, to reach a point where there is no distinction between the subject practiced and the practitioner. For this, you have to focus all your energy on the subject in order to achieve mastery.
To become one with the subject, one must go to the bīj or “seed” of the subject, from where it emerges.
The bīj of the subject is the purest state of the subject, its root. For example, in music, the root of any instrument is pure sound or in the language of Vedānta – Ōṃ (Aum). From there, everything that is called “music” emerges. Like the beej of any other subject, the bīj of music – pure sound – can be called by many names: Truth, Ultimate Reality, Existence, etc. Thus, if one goes to the root of any subject through sādhanā, one experiences ultimate knowledge or Truth. So we can also say that the highest goal of sādhanā is to experience Truth. The subject is the medium, and gaining mastery over it is the practical outcome. The sādhanā or intense practice of a subject takes the sādhak or practitioner from the material level to higher spiritual levels, where he can ultimately go to the subject’s root and experience Truth.
Truth is not something that can be taught. It is something that must be experienced or self-realized. Unfortunately, in today’s society, the education practice is such that we are given ready-made information that we have to accept rather than discovering it through our own understanding. It is a system that creates more believers than seekers.
Truth needs no belief; Truth is being. It is eternal – śāśwata. Even if Truth itself comes to you and tells you to believe, you must not believe. Because that belief will make that Truth a lie. Truth itself is not a lie, but your belief of it without experience is wrong. Truth never creates beliefs. Truth is Truth. When you have any experience, your belief turns into knowledge and that is Truth.
What are the obstacles that come in the way of experiencing Truth? The biggest obstacle is your mind. Everything – your beliefs, ideas, concepts, thoughts and information – are all the clouds that conceal the Truth from you. Until you disconnect from these things, you cannot experience Truth, as it can only be experienced in the absence of the conscious mind. It is through sādhanā that one can reach a “mindless” condition.
As mentioned before, one can do sādhanā of many different subjects. But the ultimate goal is one and the same: the experience of Truth, which occurs in a mindless condition. The three most direct paths to reach a mindless condition are yoga, music, and Tantra. It is important to understand that there is not one single path or sādhanā that everyone can do. Each person is unique and so their path is unique, but there are similar experiences that sādhak share as they move towards a common goal.