No matter how much effort is exerted, no-one can earn one cent more than G-d has ordained that one shall earn. One must do what is necessary, but one must remember that all one's work is but an accessory. The main thing is G-d's blessing, and that blessing is earned by observing G-d's commands: praying with a minyan, observing Shabbat in the best way, meticulous observance of kosher, having children instructed by pious teachers.
— Rabbi Yosef Yitzchak of Lubavitch (Hayom Yom for Av 4)