It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace.” Hebrew 6:4
The above scripture shows one can possibly lose his/her salvation. Salvation comes through believing Jesus but it is not a one-time act. It governs and defines how we should behave and act the rest of our lives. One can argue it is possible that a person might not be saved in the first place instead of saying he lost his salvation. In other words, it is easier to conclude that one salvation cannot be lost. It is easy to put the issue at the beginning of the foundation of one's Christianity that is one’s salvation rather than the type of life style one leads.
I do believe that the day of our salvation has nothing to do with what kind of life we may lead after that.
I think the lifestyle we follow every day is based on our choice to love or to hate. To listen to the word of God or not. Just like the day of our salvation we choose to obey God and give our lives to him.
There is always a time we will be tempted to revolt against God and to disobey his commandments.
Even if Holy Spirit is always with us to comfort us in times of failures and moment of disbelief, the choice is still ours to follow the path of righteousness or not.
As Paul mentioned in this place, it is always difficult to correct someone who knows all these facts but chooses to deny Christ. I don't know why someone would want to do that but the end is worse than the person didn’t know the truth in the first place.
In addition to this passage, we have several similar warnings and advices about such issues in the Bible.
See to it, brothers and sisters, that none of you has a sinful, unbelieving heart that turns away from the living God. But encourage one another daily, as long as it is called “Today,” so that none of you may be hardened by sin’s deceitfulness. We have come to share in Christ, if indeed we hold our original conviction firmly to the very end. As has just been said:
“Today, if you hear his voice, do not harden your hearts as you did in the rebellion.” - Hebrew 7-12
Here it shows that, we should fight sin and the deceitfulness of sin every day to be confident and blameless.
Jesus Christ has finished all the work that needs to be done for you and me to be saved. There is nothing left that we must do to finish the work. This means if we believe in him and die right away, we would inherit the kingdom of God.
But as long as we live in this flesh, we need to keep the good work that our Lord has started in us and be faithful to him all the time. In times of trouble and sin, we should always come to him by faith with true repentance.
Every tree that does not bear good fruit is cut down and thrown into the fire. Thus, by their fruit you will recognize them. Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but only he who does the will of my Father who is in heaven. Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name, and in your name drive out demons and perform many miracles?
Then I will tell them plainly, 'I never knew you. Away from me, you evildoers!'” - Matthew 7:19-23
Here Jesus warns anyone who thinks he can get in to the kingdom of God without first experiencing the kind of relationship God wants through his Son, Jesus Christ.
It is possible that one can prophesize, or cast out demons but not know Jesus Christ personally or do it with the wrong motive.
Now a days, this is not far from the truth. We see many do all manner of bad things in the name of Jesus but it is far from what Jesus would want or do if He were in their place. It is seriously advised here that anyone who thinks is standing should watch his steps since falling can happen any time.
These things happened to them as examples and were written down as warnings for us, on whom the culmination of the ages has come. So, if you think you are standing firm, be careful that you don’t fall! No temptation has overtaken you except what is common to mankind. And God is faithful; he will not let you be tempted beyond what you can bear. But when you are tempted, he will also provide a way out so that you can endure it. - 1 Corinthians 10:11
“Then you will be handed over to be persecuted and put to death, and you will be hated by all nations because of me. At that time many will turn away from the faith and will betray and hate each other, and many false prophets will appear and deceive many people. Because of the increase of wickedness, the love of most will grow cold, but he who stands firm to the end will be saved.” - Matthew 24:9-13
“If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, but only a fearful expectation of judgment and of raging fire that will consume the enemies of God. Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses. How much more severely do you think a man deserves to be punished who has trampled the Son of God under foot, who has treated as an unholy thing the blood of the covenant that sanctified him, and who has insulted the Spirit of grace? For we know him who said, ‘It is mine to avenge; I will repay,’ and again, ‘The Lord will judge his people.’ It is a dreadful thing to fall into the hands of the living God.” - Hebrews 10:26-31
Here it touches the main point of abusing the grace of God by living sinful life over and over again and not willing to surrender the sinfulness of the heart to the Lord.
It is understandable that one can go through an addictive way of life that is sinful and brings disgrace to the Lord. This behavior is like a bird in cage or a fish inside a fishing net which always enslaves one to the same sinful behavior again and again.
One may also ask that there is no way a believer can be addicted to sin. I would say that this is not true. As long as we are living in this flesh, we are tempted and often time defeated by the will of the flesh.
We know that the law is spiritual; but I am unspiritual, sold as a slave to sin. I do not understand what I do. For what I want to do I do not do, but what I hate I do.
And if I do what I do not want to do, I agree that the law is good. As it is, it is no longer I myself who do it, but it is sin living in me. For I know that good itself does not dwell in me, that is, in my sinful nature.
For I have the desire to do what is good, but I cannot carry it out. For I do not do the good I want to do, but the evil I do not want to do—this I keep on doing.
Now if I do what I do not want to do, it is no longer I who do it, but it is in living in me that does it.
So I find this law at work: Although I want to do good, evil is right there with me. For in my inner being I delight in God’s law; but I see another law at work in me, waging war against the law of my mind and making me a prisoner of the law of sin at work within me. What a wretched man I am! Who will rescue me from this body that is subject to death? Thanks be to God, who delivers me through Jesus Christ our Lord!
So then, I myself in my mind am a
lave to God’s law, but in my sinful nature[d] a slave to the law of sin. -Romans 7:14
Paul mentioned in this place that the spirit and the flesh are always at war. The flesh wants to do what it pleases without thinking about the consequences since it is pleasing to it.
The Spirit wants to please God and to do what is good and honorable and stay away from all forms of immorality.
There is always this battle between the spirit and the flesh and once in a while one defeats the other and this is all because we are human beings.
Moreover, there is nothing we can do to overcome this issue except throw our selves under the mercy of God with humility and broken heart.
One may ask if we are always under the umbrella of sin and grace, how can one lose his salvation?
I will leave the answer to this question to God as He knows the hearts of men. I don't even know about me. Only he knows the beginning and the end. I just want to present the truth about the characteristics of our salvation according to the Bible. It is not my intention to judge anyone here. We all are going under different circumstances and it is very clear to me that flesh always wants contrary to what the Lord wants for our lives
Moreover, I want to emphasize that our salvation doesn't come freely so we shouldn't take it for granted. Jesus Christ paid his life for us so we should never abuse the blood that redeemed us the wrath of God.
In conclusion, the concept of losing one’s salvation is directly related to the nature of relationship with our father in heaven through the fellowship of Holy Spirit. This relationship has to be worked out the way we establish and maintain a good relationship with our family and friends. It has to be taken very seriously. It has to be nourished.
It is also important to rely on the grace of God without abusing it. Those who intentionally abuse the blood of Jesus and displease the Spirit of God in whom we are destined for eternity, there is no forgiveness of sin! It is all lost! Salvation is Lost!
For such a person, it is much better that s/he were never born if s/he intentionally abused the grace of God over and over again since the grace of God doesn't give any license to sin.
May God bless you and may your light of righteousness keeps burning until He comes back in the name of Jesus. Amen!