May the Lord help you to firmly strengthen yourself by His spirit. This demands the utmost heedfulness. If inner concentration is lacking we must grieve and fall down before the Lord with pain of heart. It is not attained solely by our own efforts; on the other hand, it does not come without labor. It requires a cooperation of forces–from there and from here; this is essential. First God created light, and then He gathered it into the celestial bodies. And so it is with us. Good exists, but it is dissipated or diffused. It must all be brought together into a single unity. The soul, it seems, desires this, although evidently it does not recognize this desire. The chief obstacle is–self-pity. Lord, have mercy upon us! Without struggling and applying ourselves we shall achieve nothing. We must force ourselves at least a little bit, even if only by a hair’s breadth. When there is zeal and dedication everything goes as it should. But true zeal shows no self-pity. Is there, aside from this, a good foundation? Here it is: a profound sense of one’s sinfulness and lack of self-justification before God.

— Bishop Theophan the Recluse 

(Translated From Letters on the Spiritual Life: 1985 reprint of 1908 Moscow edition)