When you have become penetrated with the joy of God, all of your sorrows will turn into joy, all of your trials will be graces; you will recognize your faults, you will be sorry for them, and they will be forgiven so that they may become happy faults. They will remind you only of the goodness, the tenderness, the joy with which God forgives them.
It doesn't matter what is going on in our lives, we should always have joy. This does not mean to just push aside feelings and bottle them up, but we are to still have joy. Joy doesn't depend on our situation--it is continual, it is perpetual. Paul wrote the book of Philippians while in prison, but yet that book is filled with only encouragement. He isn't burdening others, he is lifting others up...with his joy.