It is certain that one’s own effort is necessary, though one cannot do the sadhana by one’s own effort alone. The Mother’s Force is needed, but the sadhak must open himself to it, reject what opposes the Force, put his full sincerity, aspiration, will power into the sadhana. It is only when all is open and there is the full surrender that the Divine Power takes up the sadhana so entirely that personal effort is no longer necessary. But that cannot happen at an early stage—one must go on opening oneself, consecrating oneself, making the surrender till that later stage comes. This has been explained in the book The Mother.
Ref: The Mother with Letters on The Mother