When we say that human efforts cannot of themselves secure perfection without the aid of God, we thus insist that God’s mercy and grace are bestowed only upon those who labor and exert themselves, and are granted to them who will and run, according to that which is sung in the person of God in the eighty-ninth Psalm: ‘I have laid help upon one that is mighty, and have exalted one chosen out of My people’ (Ps. 89:20). For we say, in accordance with our Savior’s words, that it is given to them that ask, and opened to them that knock, and found by them that seek (cf. Mt. 7:7); but that the asking, the seeking, the knocking on our part are insufficient unless the mercy of God gives what we ask, and opens when we knock, and enables us to find when we seek. For He is at hand to bestow all these things, if only the opportunity is given to Him by our good will.
St. John Cassian