Is it possible for saved people to lose their salvation?
According to Scripture, people who profess to know Christ at one time but later deny Him were never really saved to begin with. 1 John 2:19 says, "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, in order that it might be shown that they all are not of us." A true believer will never depart from the faith, so those who do so are revealing that they were never truly saved. Paul says: “being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ.” (Phil. 1:6) Scripture tells us clearly how to know if a person is really saved:
John 8:31 Jesus said to the people who believed in him, “You are truly my disciples if you keep obeying my teachings.
Heb. 3:14 For if we are faithful to the end, trusting God just as firmly as when we first believed, we will share in all that belongs to Christ.
John 13:34,35 So now I am giving you a new commandment: Love each other. Just as I have loved you, you should love each other. 35Your love for one another will prove to the world that you are my disciples.”
John 15:7,8 But if you stay joined to me and my words remain in you … My true disciples produce much fruit. This brings great glory to my Father.
Eternal life by definition cannot be temporary. If you are truly saved you have eternal life in you right now. Romans 8:28-39 clearly reveals that there is nothing in the universe that can separate true believers from the love of God. The One who chose to save you "is able to keep you from stumbling, and to make you stand in the presence of His glory blameless with great joy" (Jude 24). And praise God for it!
Some believers may lack assurance of their salvation because of personal short-comings: un-confessed sin in their lives (Psalm 51:12), lack of spiritual growth (2 Peter 1:9), insufficient prayer life (Matt. 26:41), and little time in the Word (Psalm 119:9-11,105). Once you have truly accepted the Lord your life style -- habits, hangouts, conduct, language, music, thoughts, and appetites-- should change to reflect Christ.
If your life style does not change and you continue in sin while spending little or no time in prayer and the Word, then the Bible says that you have not been saved. John writes: “So we are lying if we say we have fellowship with God but go on living in spiritual darkness. We are not living in the truth. 3And how can we be sure that we belong to him? By obeying his commandments. 4If someone says, “I belong to God,” but doesn’t obey God’s commandments, that person is a liar and does not live in the truth. 5But those who obey God’s word really do love him. That is the way to know whether or not we live in him. 6Those who say they live in God should live their lives as Christ did. “ (1 John 1:6; 2:3-6)
Being saved is a black and white matter. There is no gray area, no middle ground. Either you are saved by grace through faith or you are simply not saved at all. You can’t be almost saved or partially saved. God doesn’t play those games. He saves to the uttermost and that is the only way that God saves! The writer of Hebrews states: “Therefore He is also able to save to the uttermost those who come to God through Him, since He always lives to make intercession for them.” (Heb. 7:25)
We need to examine ourselves and make sure we have sincerely committed ourselves entirely to Him.” Examine yourselves to see if your faith is really genuine. Test yourselves. If you cannot tell that Jesus Christ is among you, it means you have failed the test.” (2 Cor. 13:5) When you are truly converted the Bible says that you become a new creation in Christ Jesus. You will stop doing the things you used to do because He changes your desires and gives you the power to live a holy life. (2 Cor. 5:17)
The Apostle Peter wrote, “As we know Jesus better, his divine power gives us everything we need for living a godly life. He has called us to receive his own glory and goodness! And by that same mighty power, he has given us all of his rich and wonderful promises. He has promised that you will escape the decadence all around you caused by evil desires and that you will share in his divine nature. So make every effort to apply the benefits of these promises to your life. Then your faith will produce a life of moral excellence. A life of moral excellence leads to knowing God better.”(2 Pet. 1:3-5)
If you are saved then the Holy Spirit lives in you and anyone indwelt by the Holy Spirit is secure eternally, because He is the "deposit guaranteeing our inheritance" (Ephesians 1:14).