He wanted to save us. Because we believed Him, our salvation is that joy. There's another cup of judgment to come on the world that still hasn't come. It's described in Revelations and we'll touch on that a little later. That just pictures trust in the Lord.
Lets go to the Old Testament for that.
Calling on the Name of the Lord means to make a sincere act of devotion in recognition of the greatness of His salvation. This pictures Christ's life, and His chosen portion which was what God had given Him. So God is His portion, His inheritance, and the One who guarded and planned His life in every detail for our Lord Jesus Christ when He was here on earth. When you think how wisely God planned every detail of Christ's life, isn't it wonderful to think that if we become His children and maintain our daily fellowship with Him, He'll do the same for us. When we complain, we show a lack of confidence in God's love and His wisdom and His power.