We cannot conceive of matter being formed of nothing, since things require a seed to start from... Therefore there is not anything which returns to nothing, but all things return dissolved into their elements.
The nature of the infant is not just a new permutation-and-combination of elements contained in the natures of the parents. There is in the nature of the infant that which is utterly unknown in the natures of the parents.
A love affair is like a short story--it has a beginning, a middle, and an end. The beginning was easy, the middle might drag, invaded by commonplace, but the end, instead of being decisive and well knit with that element of revelatory surprise as a well-written story should be, it usually dissipated in a succession of messy and humiliating anticlimaxes.