But most importance factor is determined objective of realisation of element of Divine and when there is perfect union between the devote and divine objective than realisation of element of divine become possible.

If you are unable to make mind habitual unmoved from Me, then O Arjuna! You wish to attend me by practicing Yoga. (Bhagwat-Gita: 12/9)

When mind and intelligence are unstable wondering in material world, resist strongly to uphold element of Divine. Divine God is suggesting to Arjuna that if he is unable to attend divine conscious due to lack of awaken mind he should exercise-yog to fulfil his wish.
Repeatedly focusing mind on the objective is called exercise, and by honoring element of equality while practicing with the sole objective of attending union with Divine-God is exercise-yog.
When worldly material is objective than desires of women-son, wealth-resources, prestige-appreciation, health, favorable etc., are governing factors and the objective of functions are also different (Gita:2/41), therefore such human is not able to perform yog.
In the previous stanza (12/8) Divine-God had advised to dedicate mind and intelligence here advising to perform constantly exercise-Yog to dedicate mind-intelligence. But most importance factor is determined objective of realisation of element of Divine and when there is perfect union between the devote and divine objective than realisation of element of divine become possible.
When devotee with sole objective of realisation of element of Divine chant slogan, sing religious song or meditate regularly his mind and intelligence become free from affection and hate or or in other words become pure, and attend equality conscious and mind is awaken and wish for realisation of Divine become paramount strong and desire for material-joy diminishes completely.
The delay in realisation of divine is due to ignorance of Devotee, his tolerance to separation from Divine or in other words, lack of desire for realisation of element of Divine, otherwise both devotee and Divine-God are in same place it is a matter of only realisation.