Nothing is perfect.  Even a perfect moment is never really perfect.  There is always something else that could make it "more perfect", which contradicts itself.  Even in the most perfect moments of my life there was a stress of some sort in the back of my mind.  

Enjoy the perfect moments and realize that they are transient.  Appreciate them for what they are and realize that they, like everything else in this life, will end sooner than you would like, and most often before you are ready.