Joyfulness is very different than happiness.  Happiness is how we feel when things are going the way we like them to go.  However, joyfulness is a deeper understanding that everything is going to work out in the end.  Joyfulness is tied to the hope we have in Christ that even in the worst of situations, God will be victorious in the end.  We have to choose to be joyful, not just fall into a joyful attitude.

Rejoice in the Lord always. I will say it again: Rejoice! – Philippians 4:4 (NIV)

Week 1: Optimism
Week 2: Gratitude
Week 3: Joy in Troubling Times
Week 4: Inspiration (Encouragement)
Week 5: Friendliness