This is a very controversial subject in the church today, but if we study and discern the Word of God correctly, the answer will be clear. To begin, we must first clarify exactly what it means to be born again. When a person repents of their sin, believes Christ died and rose from the dead, and confesses Him as Lord, they become what the bible calls born again, or born from above. (Romans 10: 9,10) When you are born again, your spirit has been "saved," and forgiven of sin. (Ephesians 4:24) The Holy Spirit actually gives you a new spirit. Your old spirit, which was separated from God since birth because of inherited sin, has now been replaced by your new spirit, one created in righteousness. (Ephesians 4:24) Your body on the other hand, is still subject to sin and death and it will not be given immortality until the resurrection, but for now, it has yet to be redeemed. (1Corinthians 15:52-54)
After you are born again, it is still possible for you to sin, but only in your body and mind/soul. The part of you that has been born again, your spirit, cannot sin because it is born of God. "Whosoever is born of God doth not commit sin, for his seed remaineth in him and he cannot sin because he is born of God. (1John 3:9) Many will attempt to add to this verse by saying it really means we don't habitually sin after we are born of God, but nowhere from the Greek can you justify that the word habitually should be inserted here. This verse simply means that within your new spirit your eternal life is secured, where the seed of God is, where the Holy Spirit now dwells within you. Right now, your spirit is the only part of you that has been born again and has received eternal life. People often say, well, I believe God said He would never leave or forsake us, but I believe we can leave God. My response? So, just how do you leave God? If His Spirit abides in you, can you run fast enough to leave Him? Can you make His Spirit leave your body? The truth is, you cannot. At the moment of your new birth, God's Spirit comes to abide in you, and He said, I will never leave or forsake you. (Hebrews 13:5) So if someone claims they can leave God and thus lose their salvation, they are essentially saying they can make God's Spirit leave their body. Nonsense.
It is God who saved us, and it is God who keeps us. We should be thankful for that. In other words, backsliders are still a child of God, a disobedient child perhaps, but still God's child nonetheless, because Christ has purchased us with His blood. We are His possession now, no longer our own. (1Corinthians 6: 19,20) Do you really think that YOU have the power to take something away from God? Those who think they can take something away from God who bought us with His own blood are simply not living in reality. God wants you to know and understand that your eternal life is secure in Him. He doesn't want you always wondering if you are living up to His standards, always wondering if you are living righteous enough to stay saved, because the truth is, you cannot live up to God's standards, and that is precisely why Christ kept the law for us. (Romans 10:4) That is why, when we put our faith and trust in His redemptive work on the cross, we are eternally secure...in Him. Now, just because your eternal life is secure in Christ, doesn't mean that you are free to continue sinning and disobeying God, because although your sins are forgiven, He will still bring your works into judgment one day. You will reap what you sow while in your body. In other words, if you rob a bank, you are still going to prison! You will just be a "Christian" inmate.
If you abuse yourself with substances that you know are harmful to your body, your body will react accordingly, sometimes with fatal results, so please be careful. Understand, grace is not a license to sin and we will still be held accountable for what we did in our body after salvation, for rewards or lack thereof, so please keep that in mind. (1Corinthians 3:10-17) Now, the act of being born again is a supernatural event performed by the Holy Spirit. He is the one who has sealed you unto the day of redemption. (Ephesians 4:30) The Greek word for sealed there is sphragizo, which literally means for security or preservation.. Eternally secure, get it? We cannot possibly undo something supernatural that God did within our spirit at the time of conversion, simply by sinning in the flesh. In other words, it is impossible for you to become unborn again.
The scripture says Christ bought us with His blood, (1Corinthians 6:20) and neither you, nor I, nor anyone else can take that away from Him. To think any different is just nonsense. "He that hath the Son hath life, and he that hath not the Son of God hath not life." (1John 5:12) We know that we have passed from death unto life, because we love the brethren." (1John 3:14) These things have I written unto you that believe on the name of the Son of God, that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God." (1John 5:13) "I give unto them eternal life and they shall never perish, neither shall any man pluck them out of my hand." (John 10:28) If you have been born again, if you believe Christ rose from the dead and have confessed Him as Lord, your eternal life is secure. (Romans 10: 9,10) Don't let anyone tell you any different...