Revelation 20:4 speaks of a future judgment for the unbeliever. The point as it relates to this verse and the topic of this Psalm is that God is going to judge people who do claim to worship Him. There is going to be a tough judgment on those who just "go through the motions". Some may ask, "Is it fair that a person has to suffer eternally for just the things they have done in this lifetime?" People suffer eternally based on the fact they have refused to receive God's free payment for sin, which is Jesus.
The problem with most people is they feel they have to earn or merit God's forgiveness by showing how good they are. They think by having enough works or discipline that they can get into heaven. God on the other hand says in effect, "I know what you are really like on the inside and I'm not impressed by all of your effort to cover your sins. Since I God am offering my "only begotten Son" (see John 3:16) for your sin payment, why would you want to try to top that by turning from sin based on your own effort?"
Rest assured, God is a perfectly just judge who will judge all people fairly and His judgment is certain.