Through intensity and steadfastness in practice, a fusion of the being's (or the jeeva's) heart & mind happens with the "Param Brham" or the Supreme Absolute. When this happens, Brham starts manifesting within the being's heart & mind - slowly but surely transforming the being into an enigmatic ecstatic state of involution. This process is that of Yoga or integration and results in "Kaivalya" or oneness.
The being stays the being, Brham stays Brham - but they also become one point and one flow.
This involution or "turning inside" of the mind in the pursuit of it's own Self is the beginning of meditation. When the inner intensity of this involution becomes so extreme that even the light of the Self is penetrated through, one reaches and dwells in the supreme truth in the region of the Brham. The being becomes sinless, guiltless, pure and free irrespective of his worldly condition.
This involution is also the true surrender in its highest sense. You can go to hundreds of holy men and fall at their feet but unless this inward journey has started within you to know that which is the only and the eternal pursuit of all the realized beings that have walked before us, you have not surrendered.
When the Yogi, the integrator, turns his mental gaze inwards (physical closing of the eyes is not necessary), to penetrate the nature of his very own Self and to rediscover the Holy Supreme Absolute from where he sprung forth from, he accumulates spiritual potential. This is similar to a stone on a slingshot. The more you pull the sling back, the more power it accumulates. When such a Yogi turns his mental gaze outwards it pierces through the ignorance of whoever comes into his attention span - creating realization even in the dullest of minds.
This is the will power of the Yogi which is mostly directed inwards in the pursuit of his own Self and his ultimate Guru, the Holiest of the Holy Supreme Absolute - Shree Param Brham. A fraction of this will power is directed towards the welfare of the other beings under Karmic motion in the relativity container of Maya or the Cosmic Delusion. This will power becomes grace because while it is directed outwards, it is propelled from the deeper realms of reality - it doesn't have a purpose of its own.
Develop intensity in your practice no matter what you do outwardly. Achieve the speed of inner light so that you can see the light of the Self. Then develop more intensity to surpass the Self, so that the Self exists no longer and you take your first true step into the Brham, the Supreme Absolute.
"But why should I undertake this journey?"; if that's your question, then this article has no meaning for you for now.
All the best,