We take happiness for granted. It's like we think we deserve it. But we don't. Ultimately we deserve hell. Christ changed that by suffering the wrath of God in our place so that we can experience the joy of eternal life.
Happiness is temporal but joy is found in the eternal.
So we should be joyful...when? Only when we remember what lies ahead (in heaven)? Or how about when things are going our way? Rejoice in the Lord every-once-in-a-while? No. "Rejoice in the Lord always: and again I say, rejoice." (Phil. 4:4)
The little pains and frustrations that you experience here on earth are nothing compared to what was in store for you before Christ stepped in and took your punishment upon Himself. Even the things that you consider to be "big" (losing your job, bad health, death) are nothing in the face of eternal death versus eternal life.
Earthly circumstances do not and will not change the eternal joy of Christ's salvation.
Habakkuk 3:17-19 "Although the fig tree shall not blossom, neither shall fruit be in the vines; the labour of the olive shall fail, and the fields shall yield no meat; the flock shall be cut off from the fold, and there shall be no herd in the stalls: Yet I will rejoice in the Lord, I will joy in the God of my salvation. The Lord God is my strength, and he will make my feet like hinds' feet, and he will make me to walk upon mine high places. To the chief singer on my stringed instruments."
Habakkuk's whole world was falling apart as he was experiencing all kinds of pain and inconvenience yet he rejoiced. His joy was found in the Lord.
You and I really have no excuses.
Glory in the Lord, trust in the Lord, rejoice in the Lord. Thank Him for the pain and the pleasure.
1 Chronicles 16:10 "Glory ye in His holy name: let the heart of them rejoice that seek the Lord."
Short 'n sweet