From the teachings of Swami Sivananda Saraswati

Mental abstraction takes place when the mind is disconnected from the indriyas. When the indriyas give up the objects, they take the form of the mind-stuff. They are drawn into the mind. This is termed pratyahara or abstraction. When the indriyas are withdrawn from their respective objects, it is indriya-pratyahara.

Pratyahara is a general, broad term which includes dama. The effect of dama, restraint of indriyas, is pratyahara. If you can practise consciously pratyahara at will, consciously attaching and detaching the mind to and from the senses, you have gained really a great control over the mind. You can check at any time the outgoing tendencies or outgoing forces of the mind. Pratyahara is the stepping-stone to inner spiritual life. He who has succeeded in pratyahara can concentrate his mind quite readily for a very long time. Dharana and dhyana come automatically if pratyahara is perfected.

An aspirant has to struggle hard to have mastery over pratyahara. Perfect vairagya is indispensable for success. You can succeed after strenuous and incessant struggle for some years. It is said in the Yoga Sutras of Sage Patanjali (2:55):

Tatah parama vasyatendriyanam.

There is highest mastery over the sense organs (by pratyahara).

Do’s and don’ts

If pratyahara is perfected, all the organs are under perfect control. During the period of sadhana, do not mix much; do not talk much; do not walk much; do not eat much; do not sleep much. Observe carefully the five ‘do-nots’.

Mixing will cause disturbances in the mind. Talking much will cause distraction of the mind. Walking much causes exhaustion and weakness. Eating much induces alasya and tandri, laziness and sleepiness.

If you have the reins of the horses under your control, you can have a safe journey. The indriyas are the horses. If you have the senses under your efficient control, you can have a safe journey on the path of moksha. Indriyas cannot do anything without the help of the mind, their master and commander.

Control of the indriyas means control of the mind only. Control of thoughts leads to the control of the mind and indriyas. It leads to the attainment of infinite bliss and eternal life. Therefore, control of thought is indispensable.