Bhagavad-Gita The Song Divine Chapter 6 (stanza 12-23)

And, occupying that seat, concentrating the mind and controlling the functions of the mind and senses, he should practice Yoga for self-purification. ………… (12)

Holding the trunk, head and neck straight and steady, remaining firm and fixing the gaze on the tip of his nose, without looking in other directions. ………………. (13)

Firm in the vow of complete chastity and fearless, keeping himself perfectly calm and with the mind held in restraint and fixed on Me, the vigilant Yogi should sit absorbed in Me.  (14)

Thus, constantly applying his mind to Me, the Yogi of disciplined mind, attains everlasting peace, consisting of Supreme Bliss, which abides in Me. …….. (15)

Arjun, this Yoga is neither for him who overeats, nor for him who observes complete fast; it is neither for him who is given to too much sleep, nor even for him who is ceaselessly awake.  ……… (16)

Yoga, which rids one of woe, is accomplished only by him who is regulated in diet and recreation, regulates in performing actions, and regulates in sleep and wakefulness. … (17)

When the mind which is thoroughly disciplined, gets riveted on God alone, then the person who is free from yearning for all enjoyments is said to be established in Yoga. ….. (18)

As a flame does not flicker in a windless place, such is stated to be the picture of the disciplined mind of the Yogi practicing meditation on God. ……. (19)

The state, in which the Citta (mind-stuff) subdued through the practice of Yoga, becomes completely tranquil, and in which realizing God through subtle reasoning purified by meditation on God, the soul rejoices only in God. ……… (20)

Nay, in which the soul experiences the eternal and super-sensuous joy which can be intuited only through the subtle and purified intellect, and wherein established the said Yogi moves not from Truth on any account. …….. (21)

And having obtained which he does not reckon any other gain as greater than that, and established in which he is not shaken even by the heaviest of sorrows. ……… (22)

That state, called Yoga, which is free from the contact of sorrow (in the form of transmigration), should be known. Nay, this Yoga should be resolutely practiced with an unwearied mind. ……… (23)