Musar su Salmi 113:5

The matter of holiness is dual. Its beginning is service [of G-d] while its end is reward; its beginning is exertion while its end is a [divine] gift. That is, its beginning is that which a man sanctifies himself, while its end is his being sanctified. This is what our sages, of blessed memory, said: "if a man sanctifies himself a little, he becomes much sanctified. If he sanctifies himself below, he becomes sanctified from above" (Yomah 39a).