It is not indispensable that the Grace should work in a way that the human mind can understand, it generally doesn’t: it works in its own “mysterious” way. At first usually it works behind the veil, preparing things, not manifesting. Afterwards it may manifest, but the sadhak does not understand very well what is happening. Finally, when he is capable of it, he both feels and understands or at least begins to do so. Some feel and understand from the first or very early; but that is not the ordinary case.
Ref: Letters on Yoga – II