Joy is a rare commodity.  It is not just a happy emotion; joy is the overwhelming gladness which stems from everything being right and expresses its energy in worship and godly activity (Romans 15:13).  It is the natural condition of heaven.  The 19thC pastor/evangelist, F B Meyer, wrote that ‘Joy is peace dancing; peace is joy at rest’.  Both are essential for spiritual health and only come from receiving forgiveness and new life from God, because of Christ’s atoning sacrifice through the indwelling Holy Spirit (Acts 2:38).
 
The ascension of Jesus was not a sad departure because, at last, the apostles had understood God's plan.  They saw how the words and work of Jesus exactly fulfilled the prophetic Scriptures, and believed that they and the church would be empowered by the Holy Spirit to carry on the gospel work.  So, when Jesus blessed them and went up through the clouds, they knew their commissioning (Matthew 28:16-20) was complete (Acts 1:7-9).  Instead of grief at His going, they were joyful because they knew that it was absolutely right and they were assured that He would come again (John 14:3).  Angels confirmed His Word even as they saw Him go (Acts 1:9-11).
 
Their worship was full of joy too, and it did not fade when they went back into the city.  The apostles were full of hope.  They were sure that nothing was amiss with God's plan and accepted the responsibility of spreading the gospel.  Until the resurrection and Jesus’ explanation of God’s Word, they did not understand what God was doing, or how Jesus was a part of the Divine strategy.  Now they knew.  True, they would have to wait for the Holy Spirit to give them boldness, and they did not really know how all that would come about (Acts 2:1-4).  But they now trusted the words of Jesus, their own observation of Him and the Scriptures which explained what God was doing.  Far from everything being desolate, they knew there was everything to strive for and look forward to.
 
Perhaps the church needs to recover this tripod of truth: firstly, learn how to understand what the Bible says about Jesus; secondly, how to trust Jesus personally and dynamically with the Spirit's help; and, thirdly, how to interpret personal experience in the light of our living relationship with Christ and the explanations of the Scriptures.  In the same way that a tripod is a secure structure, so these three doctrinal elements keep Christian believers secure and joyful.  Remove any one of them, and the believer becomes unstable in heart or mind or both.  So, stay true to the Scriptures, believe that the Lord will stay true to you and measure the rightness of your experiences and circumstances by what He says rather than what you think.  That sort of security will enable you to keep productive in the hard times, endure persecution, witness with boldness, be ready to answer questions about your faith and to worship with joy.  And may God bless you as you live that great adventure with Him until He comes again.