Tapasya is often translated as "austerity," but its etymological root, tapas ("deep meditation"), indicates a process of purification by which you make yourself more seasoned and mature.
Tapasya includes control over one’s physical body, speech, thoughts and mind. It helps an individual meditate properly, control the ego, and create a disciplined mind that will not accept the desires of the body.
Pranayama and meditation are also important forms of tapasya as they ignore distractions and involve focusing entirely upon God or the breath. A person who practices tapasya (a tapasvisn) should also practice vegetarianism and pure non-violence toward all living beings. This eliminates anger and destructive impulses so that one avoids the foolishness of hurting others.
Consistent yoga practice is considered tapasya because it requires discipline, self-control and denial of bodily desires. Patanjali, the ancient authority on yoga, taught that realizing the full meaning of yoga requires tapas, svadhyaya (study of the self), and ishvarapranidhana (reflection on God and the oneness of the universe).