Sri sage Patanjali says in Patanjali Yoga Sutras:
“Sthiram sukham aasanam” (2.46)
Sthiram – Firm Sukham – Comfortable or happy
One has to be comfortable and firm in aasanas, not to force oneself into an uncomfortable position. In the beginning it seems difficult but with time and practice everything is achievable.
Intelligence needs to be steady and not to roam in toughts. Spirit needs benevolence, to be good in thought and understanding of the aasana practiced.
“Tasmin satishvaara prashavaasyoha gativicchedaha pranayama” (2.49)
Pranayama is regulation of the incoming and outgoing breath, with retention.
Prana– Vital life force (chi in chinese)
In Pranayama one should breath comfortably, not heavily or with force, hold the breath inside as well as outside, and exhale all with precision due to duration and place.
Pratyahara means controlling the senses (or Indriyas). Once you follow the Yama and Niayama, all your sense organs come under your control. Once this happens, your mind will search for stimulus, ‘entertainment’, and it can roam outside to find its satisfaction(in worldly things). You can control it, and ‘entertain’ it using scriptures, positive thinking, and self-enquiry.
Dharana means concentration. Keep the mind concentrated on assimilating the knowledge. The functionality of the mind will make it roam around; our mind wants to ‘entertain’ itself by the Indriyas (senses). Our effort must be to bring it back to the focused object of concentration.
Dhyana means meditation. Meditation is focusing the mind on one object alone! Keeping the mind one-pointed on an object, for a length of time. If the mind is concentrated but then roams around after five minutes, meditation will never take place. Sri Swami Sivananda says that the minimum time sitting in meditation pose, and practising concentration, should last for at least 25-26 minutes. Only then can one attain meditation.
Samadhi is the ultimate happiness, total bliss.You become one with the Supreme Soul. There are two kinds of Samadhi: 1. Savikalpa Samadhi, 2. Nirvikalpa Samadhi.
Savikalpa Samadhi is happening while there is still duality and division. In contrary, Nirvikapla Samadhi is when unity is present, when there non-duality. For example, when you see all the gods in India, you believe them to be many (Sarvikalpa Samadhi), but once you are in Nirvikalpa Samadhi, you acknowledge that they are all one!
Only in Nirvikalpa Samdhi one can burn his karmas, and break the wheel of Samskara (life and death cycles).
*Special thanks to my Yoga teacher Bhoomaji Chaitanya, to my philosophy teacher Swami Yogeshananda Saraswati, which many of the information above has been learnt.
*Information taken from: Sri Swami Sivananda books, and his disciple Swami Venkatesananda.