Sadhana is practice with a single-minded aim
which helps to prevent suffering
Pantajali said it, the Buddha said it, human life is full of suffering. This suffering is caused by our attachements to what is inherently impermanent and everychanging. We believe that our happiness or pain is attached to external conditions that never stay the same despite our efforts. This state in yoga is called “avidya” meaning devoid of knowledge. Vidya, knowledge emerges when we realize that we are not truly this small suffering being that we take ourselves to be but instead a luminous being of light connected to an infinite Universal Consciousness.
The experience of Oneness, of Truth, of Liberation from the push and pull of the dualities of the external world can only be accomplished through the physical form of the human body. And yet, the body creates much of the impediments that cause us to suffer and stray off our spiritual path.
It gives me a ray of hope that all the impediments to a spiritual practice have been written down and acknowledged by Patanjali in the Yoga Sutras. What this demonstrates to me is that I am not alone in experiencing them, and as a result I am not alone in be able to overcome them. The impediments described in the Yoga Sutras are: vyadhi (disease, sickness), styana (procrastination), samsaya (doubt in the method), pramada (carelessness, neglect), alasya (laziness, sloth), avirati (sensuality, craving), bhranti darsana (misconception, illusory knowledge), alabdhabhumikatva (failure to obtain one's goal), anavasthitatva (inability to maintain the state attained, backsliding).
1.32 Tat pratisedhaartham ekatattva abhyasah
Concentration of a single purpose should be practiced; only such practice can counteract the distracting power of the impediments (to yoga) - Gitta Bechsgaard, The Gift of Consciousness
The impediments result in physical pain and suffering, mental depression and anxiety, and irregular flow of breath and life force. But, there is a light at the end of the tunnel! The remedy to working with the impediments to practice is adherence to a single-minded effort. To overcome distractions and imbalances, one must have a one-pointed focus or aim, an objective. This is Sadhana or devoted practice. One could say relentless passion and vigor towards one aim. In yoga, the goal, the aim is an interal one, Self-realization. When all of our energy is directed towards this aim then the impediments described above begin to fall away as one's consciousness becomes transformed.
It is not that you do not still experience suffering: you will still get sick, you will still feel sad, you will still feel lazy at times but your body and mind develops a resilience to bounce back quickly. When you experience these side effects to the single-minded practice of yoga like physical health, mental well-being and contentment, doubts regarding the method begin to fall away and faith in the practice become firmly entrenched. Once faith is embedded in your consciousness, it becomes more difficult to sway you off the path.
But, this journey must start step by step. Regular and uninterrupted practice over a course of time. You might say then, “but I have a full-time job, or kids, or other life responsibilities”. So did B.K.S. Iyengar. He chose to live the life of a householder, a common man, to demonstrate that it IS possible to practice and transform our lives in the midst of life. If you have a lot of life responsibilities, then your progress might be a little slower, so what! You will still experience the boons of yoga and when the time is right you will have built up all that practice to take the next step in your spiritual journey.