In contemporary theology, evangelists find that those to whom they have recently begun to disciple have a walk with God that was short-lived, it just sort of fizzled out when they grew tired of church. Evangelists see those who they spoke to on the street and convinced to recite the Sinner’s Prayer, or peer pressured them to speak with angelic tongues, and then they wonder why they find out that this person has not been attending church and just showing no growth at all. So they might say that this person has lost salvation; at one point they were truly saved, but now they have strayed away from salvation. Is that true, is it possible to lose salvation?
I think it may be the case that sometimes we will think that somebody lost their salvation because we do not teach the gospel correctly. In the place of repentance preaching, we will tell people to speak with angelic tongues, or accept Jesus into your heart, or respond to a big alter call, or any of the other evangelistic tactics that the church often applies. 
So a person in the street will begin to speak in angelic tongues, and we presume that they have been filled with the Holy Spirit, but they do not show growth or desire to do the will of God, and eventually just leave the church. Since we believe that they were once saved, we assume also, based on observation, that they have lost their salvation.
Now this is not how everybody comes to believe that it is possible to lose their salvation, but I do maintain that this is one source for coming to know this doctrine. Religious leaders teach a particular plan of salvation, people fulfill it and then fall away, thus people must be able to lose their salvation. I think many come to believe that it is possible to lose salvation, based on observation rather than what the Bible says.
So what does the Bible say? I think this essentially comes down to what it means to be baptized by the Holy Spirit, and the promise of God.
Baptism Of The Spirit
The Holy Spirit literally indwells within men, rendering salvation and guiding them on the narrow way, which is why Jesus told us that “Anyone who believes in me may come and drink! For the Scriptures declare, Rivers of living water will flow from his heart.” Anyone who truly puts their trust in Christ has Spirit in them.
Galatians 5:22-23 says that the fruit of the Spirit, (the result of this salvation and indwelling of the Holy Spirit) are love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control. After we receive the Spirit, these things begin to fall upon us as we mature in our Christian life. Jesus said that those who do not produce good fruit are none of his, and in fact, if you do not produce the fruit of the Spirit, you prove that you do not have the Spirit (Matthew 7:16-20).
Therefore, those who commit apostasy are not saved people walking away from the church, but rather they are people who were never saved in the first place. That is why John (1 John 2:19) wrote, “They went out from us, but they did not really belong to us. For if they had belonged to us, they would have remained with us; but their going showed that none of them belonged to us.”
But for those who do bring forth good fruit, the Spirit does work within them and keeps them on the path of righteousness. While everybody does sin, and in their flesh attempt to stray into the world, the Spirit rebukes, disciples and corrects them, so that they will walk on the way of righteousness. This is reflected in Hebrews 12:8 which tells us “If you are not disciplined—and everyone undergoes discipline—then you are not legitimate, not true sons and daughters at all.” Essentially, those who truly have been baptized by the Holy Spirit are guided by the grace of God to do righteousness. Therefore it is impossible for those who truly have the Holy Spirit to fall away from grace, because the Spirit does not let them.
But the significance of Hebrews 12:8 is even greater than that, because it says that those who do stray away are not legitimate, which is precisely what I am arguing. Those who are kept in the godly way by the Spirit are children, but those who stray away and are not corrected by the Spirit are bastards; illegitimate children.
Christ’s Promise
Christ promised that all of those who have truly been born again have inherited eternal life (John 3:16, 5:24, 10:28). They are children of the promise of God. God has promised that those who have been reborn will inevitably be justified and glorified (Romans 8:29-30), and that nothing can separate them from the love and salvation of God (Romans 8:31-39). As such, if a person is born again, and loses their salvation, is to make God go against the promise that he gave to them. God promised eternal life, and he did not keep that promise.
In response to this, most people will say that our covenant with God depends upon our continued obedience. We have the free choice to continue in salvation or walk away from salvation. But this is just not a biblical concept. If it were the case that men were breaking their covenant with God, that would mean that men are, in and of themselves, walking away from their salvation. But if that is the case, that means that men are, somehow, doing something to sustain their salvation.
This certainly brings into the question the relationship between the grace of God and the salvation of men. Apart from the grace of God, men cannot be saved (Ephesians 2:8-10, John 1:12-13), and cannot do anything to merit the justification of God. In contrast, if men can walk away from their salvation by their own will, that means that their own will is what is sustaining their salvation. Therefore it seems to me that to reject eternal security may lead to a system of salvation by works.
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