It is a mistake to dwell too much on the lower nature and its obstacles, which is the negative side of the Sadhana. They have to be seen and purified, but preoccupation with them as the one important thing is not helpful. The positive side of experience of the descent is the more important thing. If one waits for the lower nature to be purified entirely and for all time before calling down the positive experience, one might have to wait for ever. It is true that the more the lower nature is purified, the easier is the descent of the higher Nature, but it is also and more true that the more the higher Nature descends, the more the lower is purified. Neither the complete purification nor the permanent and perfect manifestation can come all at once, it is a matter of time and patient progress. The two (purification and manifestation) go on progressing side by side and become more and more strong to play into each other’s hands—that is the usual course of the Sadhana.
Ref : Letters on Yoga Vol. III