As long as I am talking about the "mercy seat" that was in the holy of holies where the priest took the blood of the sacrificed lamb each year, let me run you back to the Old Testament where the directions were given to Moses for building it.  Exodus 25: 17a, 21a "And you shall make a mercy seat of pure gold…and you shall put the mercy seat above, upon the ark; and in the ark you shall put the testimony that I shall give you."  (The ark is another story)

And here is the good part:  Ex. 25:22  "And there I will meet with you, and I will commune with you from above the mercy seat…"  That's where God would be.  Above the mercy seat.

The people had to go to the tabernacle--which was a huge, huge, tent--to meet with God.  And they couldn't even go into the holy place.  Not like now.  We get to talk to Him wherever we happen to be.  We can ask for mercy any time we need it.  But mercy is always granted because of the blood of Christ.

Sin.  It has always been a problem for us.  We don't want justice,  We want mercy.  And since the veil was ripped open, We can go to the mercy seat of God immediately, We don't have to wait a year.  Because Christ died for me and paid the penalty for all my sin, I am a joint heir with Jesus.  God is now my Father. What a deal.  (However, the assumption that God makes is that you will quit committing known sin.  You don't go get mercy so that you can keep doing wrong over and over again.)

Read the 24-26 Chapters of Exodus.  The Holy of Holies was very, very important.  God knew that someday he was going to open it to those who accepted his Son.  The men who built it didn't.  Jesus hadn't come yet.  But remember, you can't go in unless you have accepted the blood of Christ as a covering for your sin.  And to do that, first you have to repent.  Saying "I'm sorry," isn't repentance.   (Yes, I'm going to connect all of this to Peter.  I just needed to give you some background.)