The Holy Spirit reveals what Christ has done and shows it to us. His work is finished. The Holy Spirit testifies of Christ's work on the cross and resurrection.
The word "sealed" is a permanent reality. Sealed for the day of redemption. Jesus said the Holy Spirit will be in us forever. John 14:16 Jesus is not a liar. Christ Himself and what He has done saves us by His grace through faith when we hear the message of Him. Eph. 1:13
My goodness - it is no wonder the Lord said to a man one time "I am sending you out as a missionary to the unbelieving Christians to repent and start believing in Me and what I have done for them in My love and grace."
The problem with the above is a the one of a permanent contract with
no bail outs.
Entering into the Kingdom is equivalent to a new plant shooting up in soil.
If fed and watered it lives and grows, but if not it can shrivel and die.
Why is this so hard to accept? While you have faith you are alive, when
this leaves you, you have spiritually died.
The dilemma is many see saw through their life, and the emotional discussion
with the Lord is complicated and long drawn out.
Maybe there is a state where people still have faith or a belief in God but find
the internal conflicts too much and need a time away, to live and learn rather
than be in the hot house, however that works.
So we have a mystery as to when we are sealed, and how this works in us.
I tend towards it is a mystery, and each ones walk is different, so praise the
Lord.
What is wrong is to put a belief on just touching the Kingdom is salvation,
where this is just a taster of what might be, you need to jump in and dwell
in this place.