“So basically, there is security in your faith as a Calvinist. One of the many reasons I reject Calvinism.”
It’s a security wrought from the Bible, which declares that whoever leaves the faith, was never a part of it to begin with:
1Jn_2:19 They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
But the false premise of your argument is that men are justified by a mere intellectual assent, which, in that case, even Demons could be said to be believers. The faith in Christ that a believer has is founded within the heart, and shews itself by its new way of living. This person may not be perfect. This person, indeed, may be a rotten sinner, who every day fails, but his faith is such that he can cry out, like Saint Paul, with the following words:
“For we know that the law is spiritual: but I am carnal, sold under sin. For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. If then I do that which I would not, I consent unto the law that it is good. Now then it is no more I that do it, but sin that dwelleth in me. For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. For the good that I would I do not: but the evil which I would not, that I do. Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me. I find then a law, that, when I would do good, evil is present with me. For I delight in the law of God after the inward man: But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. O wretched man that I am! who shall deliver me from the body of this death? I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.”
(Rom 7:14-25)
One can know a Christian by the degree he hates himself, and despairs of himself, to never be saved by his own working and willing, but gives it all to God as the source and author of his salvation.
Indeed, and thus lives it out. Versus those who trust their merit and or church, or that God will save them in His mercy but not on Christ's account,
To the praise of the glory of his grace, wherein he hath made us accepted in the beloved. (Ephesians 1:6)