"Man does not possess strength of his own, nor can he resist the devil by himself, nor drive away sinful thoughts from himself, nor do the will of God, nor keep His commandments, nor stand against the passions.
The only thing within his power is this: to direct his free will toward God and to pray, asking Him to deliver him from Satan and from his works, and to deign—through His grace—to come and reign in his soul.
Then the Lord Himself will accomplish in man’s soul His commandments and His will, and will entrust to him all the virtues of righteousness: true faith, active prayer, love with all the soul and with all one’s strength, hope, fasting, self-control, humility, meekness, long-suffering, perseverance, and the rest. Such a person cannot boast and cannot say to himself that he has ever done anything noteworthy; rather, he continually gives thanks to the Lord, because the Lord Himself accomplishes everything—provided that He is asked.
For persistent prayer accomplishes great deeds, whereas carelessness—which comes to people from Satan—brings much darkness and obscurity into the soul; through it the enemy turns man away from God and enslaves his mind."
Saint Macarius the Great