From FUrrow to Furrow
Said the Kobriner: "In our struggle against the Evil Impulse we are like men who walk on a field from furrow to furrow. Now they go up, now down. Likewise, there are times when men are on the top of their impulses, and times when they are under them. We must make sure that the struggle ends when we are on top."
Source: Or Yesharim
