Here are a few scriptures that are really simple and clear from the NKJV...

1)  Ezekiel 18:24 - "But when a righteous man turns away from his righteousness and commits iniquity and does according to all the abominations that the wicked man does, shall he live? All the righteousness which he has done shall not be remembered; because of the unfaithfulness of which he is guilty and the sin which he has committed, because of them HE SHALL DIE"

2)  Paul stressing this in Galatians 2:18 - " For if I BUILD AGAIN those things which I destroyed, I make myself a TRANSGRESSOR!" ( sinner? )

3)  2Peter2:20-22 - "For if, AFTER they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, ( sounds very 'saved' to me at this point )  they AGAIN entangled in them AND OVERCOME, the latter end is worse for them than the beginning. For it would have been better for them not to have known the way of righteousness, ( been saved? ) than having known it, ( after being saved? ) to turn from the holy commandment delivered to them. But it has happened to them according to the true proverb:"A dog returns to his own vomit," and , "a sow, HAVING WASHED, ( by the Blood?) to her wallowing in the mire."

4)  Hebrews10:26-31 -  "For IF we sin willfully AFTER we have received the knowledge of the truth, ( after we have been saved? ) there no longer remains a sacrifice for sins, but a certain fearful expectation of judgment, and fiery indignation which will devour the adversaries. Anyone who has rejected Moses' law dies without mercy on the testimony of two or three witnesses. Of how much more WORSE punishment, do you suppose, will he be thought worthy who has TRAMPLED the Son of God underfoot, counted the blood of the covenant by which he WAS SANCTIFIED a common thing, and insulted the Spirit of grace?" ( who? THE ONE WHO WILLFULLY SINS AFTER RECEIVING THE KNOWLEDGE OF TRUTH! ),verse30 - " For we know Him who said, "Vengeance is Mine, I will repay,"  SAYS THE LORD. And again the Lord WILL judge HIS people." ( notice here it says HIS PEOPLE? ) verse31 - "It is a fearful thing to fall into the hands of the living God!" ( especially for "His people" who are to be judged like that!! )

There's some more, but I guess this is simple enough...God Bless!