For they contradict Christ himself when he says: I have prayed for you, Peter, that your faith may not fail (Luke 22:32); and John the gospel writer when he testifies in John 17 that it was not only for the apostles, but also for all those who were to believe by their message that Christ prayed: Holy Father, preserve them in your name (v. 11); and My prayer is not that you take them out of the world, but that you preserve them from the evil one (v. 15).
As per some notes from the Free Reformed Church at Kelmscott at: http://members.iinet.net.au/~jvd/Canons/ch5art7-9.htm, we read:
THE ASSURANCE OF THIS PRESERVATION
Articles 1-8 spoke of the believer's vulnerability to sin, and insisted that even in the face of repeated fall into sin, God holds on to His own, always. These articles pointed up the weakness of the believer, the strength of God, and therefore the safety and security of the believer in God's hand. This reality does not and can not change because God is GOD.
With Article 9 the fathers move on to a new topic, focusing on how the believer experiences this delightful Gospel.
The believer may know that God's elect are always safe, but he may not always experience it that way. Human as we are, we have our doubts and questions. Should we in turn feel bad because we doubt? In Articles 9-13 the fathers shift their focus to our human reactions and responses to the wealth of the contents of Articles 1-8.
What gave rise to the mention of this element of the believer's assurance of his preservation was the following error of the Arminians: "Without a special revelation we can have no certainty of future perseverance in this life" (Rejection of Errors, No 5 - Error, Book of Praise, p.572). In their refutation of this error, the fathers made reference to "the followers of the pope," for the Arminians were re-introducing the Roman Catholic teaching that one can never be certain of his perseverance unless he receives some sort of special revelation. Although Article 9 does not elaborate on the grounds of the believer's assurance (this is the material of Article 10), the fathers simply state in Article 9 that the believer can be sure: "Believers themselves can be certain and are certain of this preservation of the elect to salvation and the perseverance of true believers in the faith."
The certainty of God's promises does not depend on how we feel. Whether or not I feel God's promises to be true is irrelevant to the fact that they are true. By the grace of God we are allowed to be sure that God is faithful to His Word and promises. In John 10:28 Jesus gave the assurance that His own shall never perish for they are eternally safe in His hand and in Romans 8:39 Paul writes that there is absolutely nothing which can separate us from the love of God. So sure is Paul of attaining the goal God has set for him, that he writes in 2 Timothy 4:7,8,18 "I have fought the good fight, I have finished the race, I have kept the faith. Finally there is laid up for me the crown of righteousness, which the Lord, the righteous Judge, will give to me on that day, and not only to me but also to all who have loved His appearing... And the Lord will deliver me from every evil work and preserve me for His heavenly kingdom." Here Paul speaks with conviction. He has not a single doubt that he will get there because he has learned from Scripture that God holds on to His own.
"This assurance is according to the measure of their faith…." The one person, like Paul for example, is strong in the Lord without any doubts, but another person may feel certain the one day, but not be so sure the next. Isn't that the reality of the Christian life? In Ephesians 4 we read how the Lord gave office-bearers "for the equipping of the saints for the work of ministry, for the edifying of the body of Christ", with this goal: "till we all come to the unity of the faith and knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ; that we should no longer be children, tossed to and fro and carried about with every wind of doctrine, by the trickery of men, in the cunning craftiness by which they lie in wait to deceive, but, speaking the truth in love, may grow up in all things into him who is the head - Christ - from whom the whole body, joined and knit together by what every joint supplies, according to the effective working by which every part does its share, causes growth of the body for the edifying of itself in love" (Ephesians 4:12-16). Here Paul characterises the Ephesians as children who need to grow; grow in the Lord. Officebearers have been given so that the children of God may grow from childhood to manhood, from small-in-assurance to strong-in-assurance, convinced that the work of God in Jesus Christ has been done not just for the benefit of others but also for my benefit.
Lest there be the thought in my mind that I doubt too much and therefore do not have true faith after all, I need to be mindful of the fact that I remain touched by the brokenness of this life and therefore my faith will go up and down. I need to grow in faith and hence in assurance, but I will never reach full maturity in this respect in this life. Many of the Psalms give evidence of saints whose assurance fluctuated. See for example Psalm 13. David, a man after God's heart, a man who loved the Lord, begins this Psalm feeling downcast: "How long, O LORD? Will you forget me for ever? How long will You hid Your face from me?" (vs 1). There certainly is no expression of joy here. Rather, David is plagued by doubt, feels distant from God, is ready to despair: "Consider and hear me, O LORD my God; enlighten my eyes, lest I sleep the sleep of death; lest my enemy say, "I have prevailed against him"; lest those who trouble me rejoice when I am moved" (vs 3,4). Yet, David immediately proceeds on a much more positive note: "But I have trusted in Your mercy; my heart shall rejoice in Your salvation" (vs 5). God Himself holds on to David in his down moments, and carries him forward again to greater assurance. So doubt is replaced by joy: "I will sing to the LORD, because He has dealt bountifully with me" (vs 6). Notice how doubt and certainty lie close together. Isn't that a normal experience for the Christian?
I can be assured that God holds on to me, but the certainty will nevertheless go up and down according to the measure of my faith - and that can vary from day to day and from circumstance to circumstance. In order to be encouraged, therefore, I must keep the promises of God before my eyes. God wants me to cling to the promise that He holds on to me, no matter what. The certainty of God's promises depends not on my feelings, but on the Giver of the promise. God is always faithful and therefore His Word of promise is my most trustworthy assurance that He will hold on to me always, even when I fall into sin, and He will preserve me for His heavenly kingdom where I will wear the crown of righteousness which He today already has laid up for me.