YES, ONCE SAVED... ALWAYS SAVED IS GOD'S PROMISE and that is the promise which keeps in the faith and trusting only in the Lord and not in my own ability..
I am quoting bible references. However the anomaly which is explained above happens when people who are not saved claim that they are saved and from their lifestyle we start wondering how such a man can go to heaven by living a life which is not worthy of God, the answer is that such a man was not saved at all. We don't know who is truly saved, only God knows the names of his children.. and those whom he brings to him.. he will in no wise cast out. God did not bring us to him because of any of our merits, did he? "And while we were yet christians Christ died for us" so God is the one who brought us to him.. and so when we were sinners and unmeritful we were brought to him.. and so after that when we are still unmeritful God will cast us out? If we never came to God because of our merit, is he going to cast us out again for our being meritless? The answer is no.. and so once those who have been brought to Christ by God, God will keep them till the end. God is the one who works out our salvation and keeps us in the faith. we are not the ones who keep our own salvation.. and hence since God is the one who keeps us we can't fall away from grace.. its true that christians can fall, but they can't fall away.. and now for the bible quotes..
“My sheep listen to my voice; I know them, and they follow me. I give them eternal life, and they shall never perish; no one can snatch them out of my hand. My Father, who has given them to me, is greater than all; no one can snatch them out of my Father's hand. I and the Father are one." [John 10:27-30]
this verse explains a lot.. who are the sheep? those who follow Jesus? A man who lives an ungodly life and continues in sin is not Jesus's sheep because he is not following Jesus. He is not heeding Jesus' voice and following him. And hence he is not among the flock. but what will happen to the sheep whom God has made his own (means the ones who are truly saved) Now, you all know what “eternal” means, however, no one can form an idea of eternity which can fully grasp its endless duration. we know that it has no end, and therefore cannot ever cease to be. If anybody said that he had eternal life and lost it, he would be flatly contradicting himself. It could not be eternal, or else he would still have it. If it is eternal, it is eternal, and there is no end to it; and thus there is an end of further argument about it. If the life that Christ gives us, when we are born again, can die, then it is not “eternal” life, or else words have ceased to have any meaning at all. In its nature, as being the work of the Holy Spirit, and emanating from God, the life bestowed in regeneration is an everlasting one. Hasn’t the Holy Spirit described us as “being born again, not of perishable seed, but of imperishable, through the living and enduring word of God.”? The life of God imparted by the Holy Spirit must live forever. And just as the gift is continuous, and it is always being given, and as it is in itself eternal life, therefore it must always exist.
-“And they shall never perish.” They have a tendency to spiritual sickness, but their Shepherd will minister to them so that they shall never perish. They are sheep, and have a tendency to wander; but their Shepherd shall keep them so that they shall never perish. Time tries them, and they grow old, and the novelty of religion wears off; but they shall never perish. Think what you will of them, “they shall never perish,” for so the promise stands.
The first statement, “I give them eternal life,” is as broad as it can be, and this is broader still-“they shall never perish.” The rule has absolutely no exception. All of the Lord’s sheep shall be preserved. Let them live to be as old as Methuselah; they shall never perish, whatever temptation may assail them. They may be tried, and troubled, and broken down, so that they may be hardly able to live; but they shall never perish. “Never” is a long day; but it is not longer than grace will last. Blessed be God, this grand promise stands firm-“They shall never perish.”
there is more to the verse.. “No one can snatch them out of my hand.” Many will tug at them, but none shall snatch them away. The devil will give many a horrible tug and pull, to get them away; but he shall never take them out of the great Shepherd’s hand. Their old friends, and the memory of their old sins will come, and tug at them very hard, and very cunningly; but the Savior says, “No one can snatch them out of my hand.”
So, first, here is their security: they are in his hand; that is, in his possession, and he clutches them, as a man holds something in his hand, and says, “It is mine.” Neither shall anyone take them away from being under his protection. Never shall they be snatched away from Christ. When he says this, he pledges his honor to preserve them, for if one could be snatched out of his hand, then the devils in hell would rejoice, and say, “He could not keep them. He said that he would, but he could not. We have managed to snatch this one, or that one, out of the pierced hand of their Redeemer.” But such a horrible exultation shall never be heard throughout the ages of eternity. “They shall never perish; no one can snatch them out of my hand.”
“If I believed that doctrine, I would live as I pleased,” says one. Then you are not one of his sheep, for his sheep love holiness, and will not love iniquity. The change brought about by the new birth is such that a man will not return to his old ways of sin and folly. This is the doctrine; and how can you make it to be an indulgence to sin? True saints never turn the grace of God into an excuse to ignore the very commands of God, but the very mention of eternal love leads them to careful obedience.
and finally..
Rom 8:35 Who shall separate us from the love of Christ? shall tribulation, or anguish, or persecution, or famine, or nakedness, or peril, or sword? Rom 8:38, 39 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
so now it is upto you to decide.. are you one of the Lord's sheep? Do you have the characteristics of his sheep? Judge yourself and repent of your sins and if you truly repent then the Lord will add you into his flock and so cry out to the Lord for mercy and do not cease till he has mercy.. and he will definitely hear your prayers.. so trust in the Lord's promise that.. whosoever comes truly to him.. he will in no wise cast out.. so pray with an earnest heart and confess your sins to God and he is faithful enough to forgive you of your sins and cleanse you from your iniquities.