...the joy, joy, joy joy, down in my heart, where?

John Piper says that, for the Christian, there is no difference between the experience of joy, happiness, glee, (insert happy word here). He says that all of the Biblical words used for these emotions are used interchangeably. While I can't, at this point, check his greek and hebrew skills, I think that he may be right. I always got a weird feeling when someone would say that Christians experience "joy" while non-christians have only fleeting "happiness".
Usually people say this when they are going through tribulation or sorrow. They say "although I can't be happy, I can have joy because I know that I have Jesus." I think this has some validity. We need to recognize the presence of Jesus during hard times. But I think that Christians can and should seek real, smiley, bubbly, happiness even during hard times.
I'm not trying to minimize the pain and struggles of life, and I realize that we need to be sensitive to people and not try to make them artificially happy when they are really grieving. At the same time, if we really truly believe Romans 8:28, we should probably be smiling more.