Y.S. 1.17 Vitarka vichara ananda asmita rupa anugamat samprajnatah
Practice and detachment develop four types of Samadhi: self-analysis, synthesis, bliss and the experience of pure being.

Y.S. 1.18  Virama pratyaya abhyasa purvah samskara seso nyah
When the mind rises to this state of yoga and remains so, the usual mental disturbances are absent.  However, memories of the past continue.

Patanjali lets us know that it is only possible to reach higher levels of yoga through the various stages of practice.  First comes concentration and meditation.  One learns to meditate on the grosser elements before being able to contemplate the subtler elements.  The mind must achieve one-pointed-ness and have been brought under complete control in order to reach the state of Samadhi.

This constitutes an understanding of the order of the universe from the formless state of consciousness to the solid state of the physical world.  The path to Samadhi starts by contemplating the physical and works back to the state of pure consciousness.

Y.S. 1. 19  Bhava pratyayo videha prakriti layanam
Inevitable because of the many millions who share the world with us there will be some who are born in a state of yoga.  They need not practice or discipline themselves.

Y.S. 1. 20  Sraddha virya smrti Samadhi prajna purvaka itaresam
But what of the rest of us?  Is there really a chance of achieving this state of yoga?  Through faith, which will give sufficient energy to achieve success against all odds, direction will be maintained.  The realization of the goal of yoga is a matter of time.