I think the key to this is many think they are saved, they sit in churches every Sunday, they do a great job of looking the part. Yet actually are not born again believers, they practice religion but there was never that relationship with Jesus Christ. Because the evidence is fruit of the Spirit or put another way the changed man. Once truly born again the progression of things is change, you are not who you were in terms of your heart. There should be some evidence of that measured by the fruit even initially but the rest will come over time.
Also while there will be some works, as we are saved unto good works. But the attributes of the fruit of the Spirit is in our attitude in Galatians 5:22-23.
Galatians 5:22-23
Amplified Bible
22 But the fruit of the Spirit [the result of His presence within us] is love [unselfish concern for others], joy, [inner] peace, patience [not the ability to wait, but how we act while waiting], kindness, goodness, faithfulness, 23 gentleness, self-control. Against such things there is no law.
If sealed unto the day of redemption means anything ( and it certainly does) I doubt a true reborn person would walk away from the faith and leave Jesus. And I even question if they could. Back slide ? Sure, but that's not walking away. No they go out from us but were never of us.