God's mercy is available to all who will call upon Him. He offers mercy to forgive you of your past sins. He offers His Holy Spirit to empower you to abstain from fleshly lusts that would drag you back into sin. He offers righteousness. Righteousness brings peace.
Peace brings joy.
Joy that is unspeakable because it is deep within your being. And from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. In this passage we can see that our Lord not only washed us from our sins, but, He also made us kings and priests unto God. In other words the plan of salvation provides you the opportunity to be cleansed of sin and to rule your body. You do not have to be under the bondage of sin any longer.