4 As far, then, as lay in our power, we have used our influence with them, as both your brethren and our own, with a view to their persevering in the soundness of the Catholic faith, Which neither denies free will whether for an evil or a good life, nor attributes to it so much power that it can avail anything without God's grace, whether that it may be changed from evil to good, or that it may persevere in the pursuit of good, or that it may attain to eternal good when there is no further fear of failure. To yourselves, too, my most dearly beloved, I also, in this letter, give the same exhortation which the apostle addresses to us all, "not to think of yourselves more highly than you ought to think; but to think soberly, according as God has dealt to every man the measure of faith."
Source: Letters (New Advent)