Philippians 1:6 (ESV): And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ. I believe in the “Perseverance of the Saints.” I also believe that if you are a “backslider” you were never truly saved. Salvation is preceded by repentance which means to completely turn away from sin. One cannot turn away when given a new nature from God and then turn back; their very nature would rebel against it. I also believe that if one is a “carnal Christian” or uses grace as a free license to sin then they are not and never were saved. When God calls the person out of their state of total depravity their eyes are opened to the things of God and can never return to the way they were before. I would go so far as to say that if a “believer” is not continually submitting themselves to the will of the Father, not continually bearing fruit for Christ, and has no love for any of their brothers/sisters then they are NOT saved. That is why I believe in Perseverance of the saints or as you say, “Once saved always saved.”
[Bible Answer] The only Scripture you cited for backing (Phil. 1:6) offers no support at all for eternal security, also called once saved always saved or the perseverance of the saints. If you check the context of that passage (Phil 1:4-7) it becomes clear that salvation is NOT the subject of Phil. 1:6! The subject is their partnership in the gospel. Therefore, Phil. 1:6 has been misused by the eternal security teachers.
Almost everything else you wrote is a direct contradiction of Scripture and/or an invalid representation of Calvinism’s fifth point, the perseverance of the saints. For example, King David backslid into adultery and murder. To say he was never saved because he backslid is ludicrous! (The same is true about Solomon turning to idolatry and Peter disowning Jesus.) You are merely repeating what you heard some misinformed preacher say or you have misunderstood what Calvinism believes. Calvinism absolutely does teach a truly saved person (one who has been regenerated) can backslide and remain saved in the VILEST WICKEDNESS! It is only sometimes that they say, if such a person doesn’t later repent he was never saved. However, the same people also teach the EXACT OPPOSITE when they recite their perverted version of the sin unto death. The way they understand the sin unto death is, the Christian backslider REMAINS UNREPENTANT and God in his holy anger strikes him dead because of his wickedness and then takes him to heaven! (What a religious fairytale!) They want it both ways. What you have written here is NOT Calvinism, but most importantly it is NOT what the Bible says. A righteous person will die spiritually if he turns to evil, according to Scripture. There are many spiritual dangers in the Christian life and he must do his own part to remain on the road to life, under saving grace.
If you want a detailed and documented refutation of eternal security, consult the 801 page volume, The Believer’s Conditional Security. This is a salvation related issue. You need to find the truth.
Cartoon is copyrighted. Used by permission.
The context of 1 John 2:19 excludes the subject of immorality and shows it refers only to false doctrine taught by false teachers. Thus the 
Another KJV error that the Watchtower Society, the governing body of the 
Some people in pride surely aren’t aware of it or its danger, for if they were they would change! To be proud is to have God against you, which means you are a sure guaranteed loser. It is much worse to be proud than to have the devil himself and all the demons opposing you since God is infinitely greater than them. Here is the warning to take to heart:
