Pathanjali Yoga sutra
Atha yoganushasanam, yogaschitha vrithi nirodhaha
Thadadrashtaha swaroopeva asthanam vrithi saropya mitharathya
When seekers do not go through the process of inner transformation and realization, they remain stagnant. On belief alone, you can convert your religion, but you cannot transform. Changing from the Bible to the Quran is not transformation, but rather, like changing clothes. The basic principle will not change, and therefore, you remain unchanged. Whether you go to a temple or mosque, both are hollow. The temple goer and the mosque goer look different outwardly, and they both dislike eachother. Their beliefs have nothing to do with reality, but just robes that clothe their minds. But, in reality, anyone can get rid of these robes at any time. The Yogasutra is not a belief, and that is why it appears difficult because our minds are used to beliefs.
Yoga is a very personal experience, and experience will not happen through beliefs, but rather finding truth is self experience. We are our own masters. Furthermore, the way you look at life defines the style of your life. You have to burn your habits, thoughts, and perceptions, to make way for the new to arrive. Only with that newness and new principle can you come into contact with reality. Until the old dies, the new cannot arrive. The newness is hidden within. In order to sprout, the seed has to come in contact with soil and water. As the seed dies to be born as a new plant, similarly the old has to die. This death of old is your new life, and this is yoga. This yoga is not a logical derivation or a religion.
You have to become the religion in your deep being, not just analyzing the knowledge (which is the functioning of the mind). All this informative knowledge is not totality, but rather, only its fragrance. But man is very logical, argumentative, and analytical, and therefore, his heart becomes hollow. That which is hidden remains closed. But the heart is profound and the centre of Being. It is whole, but the head is only a branch, one can survive without head but cannot survive without the heart.