Patanjali is believed to the compiler of “Yoga Sutras” which is considered as the most relevant book on yoga practice. As per this, there are eight limbs or stages for yoga.
Yama and Niyama are guidelines for a yogi to be in harmony with the people around him. These rules set the stage for later phases of yoga practice. Most of the yoga practitioners focus their energy and effort on Asana ( Posture ) and Pranayama (breath control). Asana help a yogi to fine tune his body and prepare to advance to the next levels. It is unfortunate that many people don’t realize they just started their journey as they master various asanas. With Pranayama and Pratyahara, yogi learn to control their breath and their by control their mind.
Once the yogi has a fine tuned the body, gained a good control over the mind from the desires of external world, he or she is ready to search for the inner most soul. Next three stages of yoga – Dharana, Dhyana, Samadhi are the stages where a yogi gets closer to the Maker. As they advance through these stages they realize his self is part of the Supreme Soul within himself. This is the moment when they realize that what they were looking for is within them.
End goal of a yogi is realization of Samadhi and all stages are steps to reach this final goal. Dhyana is the stage where a yogi starts realizing about his end goal. In this stage body, mind, breath, senses are all integrated to the object of contemplation – Supreme Spirit. This is the stage one starts to realize Heavenly Bliss.