Yog is the process of meditation,
whereas the coming into mind of any impulse
the impulse to such contemplation is moral transgression.
Straying of the mind is deviation from the path of virtue.
The unwavering resolution with which a man
rules over his mind, breath, and senses is, therefore,
the nature of goodness.
Directing the mind,
the vital breaths, and the senses towards the desired goal
the morally excellent fortitude.
Sri Krishn says in Bhagwad Geeta:
dhṛtyā yayā dhārayate manaḥprāṇendriyakriyāḥ
yogenāvyabhicāriṇyā dhṛtiḥ sā pārtha sāttvikī
“That resolute steadfastness,
by which, O Parth,
one governs through the practice of yog operations of the mind,
the life-breaths, and the senses,
yayā tu dharmakāmārthāndhṛtyā dhārayate’rjuna
prasaṅgena phalākāṅkṣī dhṛtiḥ sā pārtha rājasī
by which the avaricious man holds fast
acquisitively to obligations, wealth, and pleasure,
of the nature of passion
Firmness of will in this case is concerned primarily
with the discharging of one’s worldly duties,
acquisition of wealth, and sensual pleasure,
the three primary objects of material life,
rather than with final liberation.
The final end may be the same,
but in this case the seeker aspires to fruits and desires
something in return for his labour.
Further Sri Krishn says:
yayā svapnaṁ bhayaṁ śokaṁ viṣādaṁ madameva ca
na vimuṁcati durmedhā dhṛtiḥ sā pārtha tāmasī
“And that steadfastness,
by which the evil-minded man declines to forsake
sloth, fear, worry, grief, and also arrogance,
the nature of ignorance.”
~Revered Gurudev Swami Adgadanand jee Paramhans~