What Macbeth says seems paradoxical: life itself is a sickness from which we recover by dying, after which we will sleep comfortably. Note the alliteration of "F" sounds in "after," "life's," "fitful," and "fever," intended to emphasize the stress, anxiety, and wasted effort, i.e., the fitfulness and feverishness, involved in living. There are actually six "F" sounds in "after life's fitful fever," because the "V" in "fever" will sound like an "F."