From Martin Luther, as quoted in Come, Thou Long-Expected Jesus:

We must both read and meditate upon the nativity. If the meditation does not reach the heart, we shall sense no sweetness, nor shall we know what solace for humankind lies in this contemplation. The heart will not laugh nor be merry. As spray does not touch the deep, so mere meditation will not quiet the heart. There is such richness and goodness in this nativity that if we should see and deeply understand, we should be dissolved in perpetual joy…This must be our daily exercise: to be transformed into Christ, being nourished by this food. Then will the heart be suffused with all joy and will be strong and confident against every assault.