After 2000 years his book of the Yoga-Sutra (196 Sutras), is considered to be classic yoga reference and it is translated, published and commented on to this day. Additionally his book remains the basic text used in Yoga Schools throughout India. Now it is studied throughout the West also.
Patanjali Mahamuni is a follower of Buddha. The only difference is he has tremendous faith in Ishvar. He surrenders to God. Patanjali has put the whole theory of philosophy into practice. He teaches to go by Ashtang (8steps) Yoga. If you follow these steps you will definitely reach your goal. The steps are: Yam Niyam Asan Pranayam Pratyahar Dharana Dhyan Samadhi. To remain in the goal he has given all the hints through his Sutra.
Yoganganusthanad asuddhi-ksaye jnana-diptir a viveka-khyateh
From the practice of the component exercises of Yoga, on the destruction of impurity, arises the spiritual illumination which develops into awareness of Reality.
Self-restraints, fixed observances, posture, regulation of breath, abstraction, concentration, contemplation, trance are the eight parts of the self discipline of Yoga
Patanjali Mahamuni gives advice in his first chapter about how do the Ashthang Yoga study with regularity and perseverance.
Abhyasa vairagyabhyam tan nirodhah
The suppression by persistent practice and non-attachment.
Tatra stitau yatno bhyasah
Abhyasa is the study with full effort for being firmly established in that state.
Sa tu dirgha kala nairantarya satkarasevito drudh bhumih
It the study (Abhyasa) becomes firmly grounded on being continued for a long time, without interruption and with reverent devotion.