"This gift of [perseverance from] God, therefore, can be obtained by supplication" (Gift of Perseverance, 6, 10)
“There are some, morevover, who either pray not at all or pray coldly, because they know from the Lord’s having said it that God knows what is necessary for us even before we ask it of Him. Must the truth of this statement be given up or is it to be supposed that it should be deleted from the gospel on account of such peoplel? On the contrary, while it is a fact that God prepares some things to be given even to those who do not pray, such as the beginning of faith, and other things not to be given except to those who pray for them, such as perseverance to the end, certainly one who thinks that he has this of himself does not pray to have it. We must beware, then, lest, while we fear that exhortation may grow cool, prayer be extinguished and presumption advanced.” (ibid., 16, 39)
“The excuse would seem more just of those who say: “We did not receive hearing,” than those who say “We did not receive perseverance,” because reply can be made: "Man, in what you heard and kept, in that much you could have persevered if you had will” (Admonition and Grace, 7, 11)
"God, therefore, gave man a good will, because He made him in that will when He made him upright (i.e., justified or regenerated). He gave man assistance (i.e. saving grace) without which man could not continue in the will even if he would; but that he would, God left to his free choice. Man was able, therefore, to continue if he would, because the assistance was not lacking whereby he was able, and without which he would not be able, to persevere in holding to the good that he might will. But because he willed not to continue, certainly the blame is his whose merit it would have been if he had willed to continue." (ibid., 11, 32)
"… But those who do not belong to this number of the predestinated … [some] receive the grace of God, but they are only for a season, and do not persevere; they forsake and are forsaken. For by their free will, as they have not received the gift of perseverance" (ibid., ch 42)