David pleads with the Lord in Psalm 51, “Restore to me the joy of Your salvation…” The word here for joy is also used in John 15:11 when Jesus says, “These things I have spoken to you, that My joy may remain in you, and that your joy may be full.”
In the Psalm, David hadn’t spoken with God for a year. Keep in mind he is not asking for his salvation to be restored, but the JOY of his salvation. He would rather have never lost the joy, but he realizes he has and he prays for restoration.
Then in the passage from John, Jesus said, “These things I have spoken to you…” What things? Look in verse 9 and He says, “abide in My love.” Jesus knows that Satan will try to steal our joy. He wants to reassure us when Satan is trying to steal our joy that if we abide in God’s love, that not only will His joy remain in us, but it will remain full.
Sometimes we (or at least I) need to be reminded of the joy of being a child of God. When I don’t feel that joy, I’m pretty sure that it’s not God’s fault, but my own. That’s when I must take a cue from King David and pray, “Restore to me the joy of Your salvation.”