Eternal Security

Because my salvation is rooted in Jesus Christ, and not myself, I am a firm believer that I cannot lose my salvation. I did nothing to gain grace and can do nothing to lose it. Over the years I have spoken with many Christians who ask the question, "If you can't lose your salvation, then what do you have to say about those people who once claimed to know Christ but now deny Him or live a life totally contrary to the Bible? How can you say they are saved?" I wouldn't necessarily say that they are. But I do believe that the Bible teaches that once a person genuinely becomes a Christian, he will always be a Christian.
I am currently reading, The Baptist Faith & Message by Charles S. Kelley Jr., Richard Land, and R. Albert Mohler Jr. On page 82 eternal security is defined. The explanation given is what I believe, just written much better than I can write. So I am quoting from the book.
"Eternal security does not mean that all who claim to believe in Jesus will be saved. The New Testament contains may warnings about false belief and false believers. Jesus spoke of the human heart in terms of four soils, warning that the shallow soil appears to receive the seed of the gospel, but no real life endures (see Matt. 13:1-23; Luke 8:4-15). Some claim to follow Christ but fall away and even repudiate the faith. How do we know that these persons were never true believers? John answered that question by explaining, "They went out from us, but they did not belong to us; for if they had belonged to us, they would have remained with us. However, they went out so that it might be made clear that none of them belonged to us" (1 John 2:19).
The Baptist Faith and Message emphasizes that true Christians are those who "persevere to the end." The perseverance of believers is the evidence of true and authentic faith - faith that saves. Thus, true believers "will never fall away from the state of grace." Having been accepted by God in Christ, believers are being sanctified by the power of God. This is a lifelong process that beings with our salvation but is fully accomplished only in our glorification that is to come.
Believers sin and may even fall into grave and awful sin that brings disrepute on themselves and the church. True believers can never remain in such a state of sin and rebellion but will repent. Peter instructed believers to "make your calling and election sure" (2 Peter 1:3). This should encourage Christians to look carefully at our lives, knowing that Christ taught believers to be fruitful and faithful."