oak,
"I have read texts like Dhammapada of Buddha, writings by gurus like Yogananda, Sivananda et al.
They all emphasize the great role of concentration and will power"
Although tremendous effort and energy is needed to come to one’s enlightenment, one should be careful to cling to the idea that only effort is needed. There comes a point where even effort is to be dropped. One’s effort is needed not to come to a transformation, but to create an inner space which is prepared for it. Beyond this, the transformation happens spotnaneously by itself.
There are those who continue cycling their effort unecessarily, and miss it. There are those who have not been initiating enough effort, and then also miss it. These are two extremes.
When to initiate the effort, when to drop the effort - this is something which becomes revealed as part of the inward journey into the inescapable.