Your misunderstanding of faith and from where it originates is the cause of your misunderstanding that saints might not persevere in it. If a person has no faith, or as you suggest may not persevere in faith, then they are not saved. Faith is a gift just as salvation is a gift, both of which are by God's grace. The just shall live by faith. As James said: "Listen, my beloved brothers, has not God chosen those who are poor in the world to be rich in faith and heirs of the kingdom, which he has promised to those who love him?" James 2:5. How can a faithless person love Christ?
What about Demas, whom Paul called a fellowlaborer? He left Paul, “having loved this present world”. Was Demas saved, or was Paul mistaken when he called Demas a fellowlaborer?
I know where faith comes from. It comes from hearing the word of God (Rom 10:17).
Also, be careful when quoting scripture.
James 2:5 Hearken, my beloved brethren, Hath not God chosen the poor of this world rich in faith, and heirs of the kingdom which he hath promised to them that love him?
You added the words “to be” between “world” and “rich”. God did not choose the poor of this world TO BE rich in faith. He chose “the poor of this world rich in faith.” The meaning is the poor of this world are frequently the ones who ARE rich in faith.