Tapas means a concentrated practice, to go toward something with the utmost concentration. To undertake something with a little bit of sweat and effort is tapas. The word tapas actually comes from heat or heating up and any practice should have a little of tapas in it. The word hatha is not used by the ancient author, master, Patanjali of the Yoga Sutras. He uses the word tapas, heating oneself up, sweating a little with intense concentration, putting as much of oneself into it as possible.
The word tapas also occurs as the third of the five niyamas (2nd step of the 8 rungs of raja yoga). It means exertion of your total personality, intense concentration with a definite goal, with a certain something in front of you and pushing yourself just a little – one step more than you did yesterday. Without tapas, there is no purification. Doing asanas requires intense concentration so that one is aware of every minor, fine tissue of the part of the body that is being exercised. The purpose and goal of tapas is to attain an intense one-pointed state of mind. Until the mind is fixed on something, until that something has gone into the depths of your subconscious, that act remains separate from the body, separate from life. It is not natural, like a student driver who is very conscious of shifting the gear, holding the steering wheel, pushing the brakes, pushing the accelerator, removing the foot, watching here, looking there – there are just so many things to do. Very confusing. But by doing it over and over and over again, what happens? You are hardly conscious of what you are doing when driving.
So tapas is that attitude in life through which, by doing something repeatedly and exerting oneself repeatedly, one makes something a definite part of one’s inner mind. Sometimes an act of tapas may be undertaken just to strengthen the mind by doing something that is slightly unpleasant and learning to conquer the distinctions our minds have between pain and pleasure. It is like waking up at 6 am tomorrow and 6 am the day after tomorrow and for four days and four months and four years and discovering that your mind has the strength to do such things. After a time of doing it, it is no longer an exertion. It has now become a purification. The mind no longer has the sloth, the negligent attitude. By doing it over and over, by pushing yourself just a little, you change the habit of your mind. When you have conquered that part of slothfulness, that impurity, you can set yourself another little goal.