Revelation chapter 5 is a scene that will take place in the future in heaven. It contains the song of redeemed sinners. Part of the lyrics of their song is the following:
Re 5:9 And they sang a new song, saying: "You are worthy to take the scroll, And to open its seals; For You were slain, And have redeemed us to God by Your blood Out of every tribe and tongue and people and nation
They will not be singing this song unintelligently. That is, they will not be singing this song without knowledge as to why the Savior was slain and why His blood was shed for their redemption. They will know full well that He shed His blood for the sins that they committed.
They will recognize the fact that they were redeemed from sin. Yes, they will remember what they did but it will become the dark background upon which the redemption of the Lord Jesus Christ will shine brightly in their eyes and will be appreciated by them for all eternity.
Eternal gratitude and love will flow from their hearts to the Savior knowing who they were and what they did. In heaven, they will be well aware that they are there as sinners saved by grace.