I see salvation happening at the end of our journey in this life. I have seen far too many 'born again' folks fall away - they were 'sealed' for nothing. I also see living my faith as 'works' - doing, as the Lord taught:
Matt 7:24 "Therefore whoever hears these sayings of Mine, and does them, I will liken him to a wise man who built his house on the rock: 25 and the rain descended, the floods came, and the winds blew and beat on that house; and it did not fall, for it was founded on the rock. 26 But everyone who hears these sayings of Mine, and does not do them, will be like a foolish man who built his house on the sand: 27 and the rain descended, the floods came, and the winds blew and beat on that house; and it fell. And great was its fall." 28 And so it was, when Jesus had ended these sayings, that the people were astonished at His teaching, 29 for He taught them as one having authority, and not as the scribes.
If they truly fall away, they were not sealed. Simple mental assent of the truth of Christ doesn't save. Satan believes in that simple sense. He is not saved from the judgment that will befall him. Entrusting oneself to Christ alone brings salvation. Only God knows who has done this. Only God will reveal this in the last day.
BUT, God makes it clear we can KNOW we have eternal life now.
"These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life. (I John 5:13)"Very truly I tell you, whoever hears my word and believes him who sent me has eternal life and will not be judged but has crossed over from death to life. (John 5:24)