Sanskrit tapasyā , literally "produced by heat", refers to a personal endeavor of discipline, undertaken to achieve a goal.
Vedic scripture tells us that producing heat (tapa) or the fire that burns within - will bring insight to our soul. This heat can begin with Japa , a repetition of a mantra with or without repetition of any spiritual discipline, such as yoga postures and meditations. Your desire thermometer is regulated by japa. The wish to change or become closer to your soul is either hot or cold or somewhere in between. This temperature is the heat that can be translated to energy undertaken to achieve whatever goal you have chosen.
The repetition or japa will begin to mold thoughts, actions and awareness. The changes begin incrementally over time as we replace poor judgment with smart choices, harmful habits with constructive ones, reaction with action.
The earliest discussions of tapas, and compound words from the root tap (Sanskrit: तप) relate to the heat necessary for biological birth. Its conceptual origin is traced to the natural wait, motherly warmth and physical "brooding" provided by birds such as a hen upon her eggs - a process that is essential to hatching and birth; the Vedic scholars used mother nature's example to explain and extend this concept to hatching of knowledge and spiritual rebirth.
By doing and repeating everyday your spiritual heat – the friction within the body like the friction between sticks and stone produces the fire to dissolve and burn the negative. Within 40 days – the mind embodies new thoughts and awareness and if sitting for 11 minutes, systems in the body begin a metamorphous.
In the yogic tradition it is the fire that burns within that is needed for the student/disciple to achieve the very difficult goal of enlightenment, to foster self-control, one mindedness and focus, simplicity, wisdom, integrity.