Sometimes, one must refrain from using certain sounds—vowels and consonants—here, so that they have the maximum impact there. Of course, much depends upon the nature of the thought one wishes to express: a gently musing one may benefit from a succession of similar-sounding words because the alliteration creates a soothing effect, but to construct a climactic moment—a line that culminates in a crescendo—the sounds that produce the pivotal words must be unique.