The second part of Yoga Sutra deals with Sadhana or spiritual practice. We are made up of three layers:
1.    Karana Sarira (causal body) – composed of the spiritual sheath.
2.    Sukshma Sarira (subtle body) – comprised of the psychological and intellectual sheaths.
3.    Karya Sarira (gross body) – composed of the anatomical sheath.
The Sukshma Sarira exists between the other two. When the dualities between body, mind and soul are made to disappear, the practitioner of yoga known as sadhaka reaches the highest state of self-realization of Raja Yoga. This is not all that easy to attain. 

Patanjali tells us of the eight-fold path of Raja Yoga known as Ashtanga Yoga to be followed to reach this exalted state. The eight-fold path of Raja Yoga consists of:
1.    Yama
2.    Niyama
3.    Asana
4.    Pranayama
5.    Pratyahara
6.    Dharana
7.    Dhyana
8.    Samadhi