Needing disappointment?

I have noticed that when I am generally happy with life, it is extremely difficult to write anything meaningful. More than that, it is difficult to even have meaningful thoughts. It is even a little hard to pray. Very strange. I guess I just have to go with the flow cause I wouldn't want to be happy but shallow forever, but I also wouldn't want to be sad yet profound all the time. But why does it work that way? Why does God need to break us (or so it seems) before we can have any kind of breakthrough? Why is there joy in sorrow, or strength in weakness? What's so great about reaching our end? Is it because once I get to the end of me, I can begin to be in something (someone) infinite?