The distinction made by cognitive linguistics between conceptual metaphors and metaphoric expressions, together with Kövecses' concepts of highlighting and metaphorical utilization (2002:79-80), are very useful tools for the analysis of both plain and literary discourse. This is proved by numerous works on the field by Turner (1987), Lakoff and Turner (1989), Gibbs (1994) and Steen (1999), among many others. Taking this model and these concepts as a starting point, in this article an analysis of Shakespeare's sonnets 153 and 154 is carried out, both texts having long been considered by critics as variations on a single theme. The analysis yields illuminating results since it allows us to understand the relationship holding between two poems that, stemming from a common theme, are expressed in formally different ways. Thus, the conclusions reveal that, although the two texts are built on a small number of common metaphors, the metaphoric expressions generated by those metaphors are instantiated in different utterances in each poem, those utterances being eventually responsible for the differences in the form of the poems.