Hello @throughfaith, here's a concise statement concerning perseverance from The Westminster Confession of Faith. This is what Calvinism teaches, in part. Saints, according to Calvinism, persevere in the faith (albeit imperfectly) because of God alone, not because of anything they choose to do apart from Him, or because of anything inherent (righteousness, strength, etc.) in themselves.
Chapter XVII. Of the Perseverance of the Saints
Section I.–They whom God hath accepted in his Beloved, effectually called and sanctified by his Spirit, can neither totally nor finally fall away from the state of grace; but shall certainly persevere therein to the end, and be eternally saved.
Section II.–This perseverance of the saints depends, not upon their own freewill, but upon the immutability of the decree of election, flowing from the free and unchangeable love of God the Father; upon the efficacy of the merit and intercession of Jesus Christ; the abiding of the Spirit and of the seed of God within them; and the nature of the covenant of grace; from all which ariseth also the certainty and infallibility thereof.
Section III.–Nevertheless they may, through the temptations of Satan and of the world, the prevalence of corruption remaining in them, and the neglect of the means of their perseverance, fall into grievous sins; and for a time continue therein: whereby they incur God's displeasure, and grieve his Holy Spirit; come to be deprived of some measure of their graces and comforts; have their hearts hardened, and their consciences wounded; hurt and scandalise others, and bring temporal judgments upon themselves.
/////////////////////////////////////////
Further,
1. The privilege of final perseverance is peculiar to true believers.
2. The perseverance of the saints is not owing to their inherent strength, or to any measure of grace they have already received, but solely to divine grace. We readily acknowledge, that in themselves they are utterly weak, and wholly insufficient to withstand the numerous and formidable enemy that are combined against them; such as Satan, the world, and the corruptions of their own hearts. If left to contend with their spiritual adversaries in their own strength, they would be easily overcome.
3. The perseverance of the saints does not secure them from partial falls, but from total and final apostasy. Our Confession admits, that believers may, "through the temptations of Satan, and of the world, the prevalence of corruption remaining in them, and the neglect of the means of their preservation, fall into grievous sins, and for a time continue therein.
4. The perseverance of the saints secures the preservation of the principle of grace in their souls, though it may greatly decay as to its exercise.
5. The perseverance of the saints is secured by the immutability of the decree of election.
6. It is secured by the merit of Christ's sufferings and death, Christ "purchased the Church with his own blood." The "iniquities" of all his people "were laid upon him," and, as their Surety, "he bore their sins in his own body on the tree." He sustained the full infliction of the curse which they deserved, and "obtained for them eternal redemption."
7. It is secured by the perpetuity and prevalence of Christ's intercession. As Christ purchased his people by the merit of his own blood, so "he ever liveth to make intercession" for them.
8. It is secured by the constant inhabitation of the Spirit.
9. It is secured by the unchangeable nature of the covenant of grace. This covenant, being founded in the grace of God, and not in our obedience, is "ordered in all things, and sure." The tenor of this covenant is clearly expressed: "I will make an everlasting covenant with them, that I will not turn away from them, to do them good; but I will put my fear in their hearts, that they shall not depart from me." Jer. xxxii. 40.
~Shaw, Robert, Exposition on The Westminster Confession of Faith, Of the Perseverance of the Saints, excerpt
~Deut