Enjambment occurs sparingly times in "My Heart Leaps Up." As a short poem, the enjambments serve both to dramatize and accentuate certain lines while adding a sense of cohesion to others, expanding phrases over the line breaks to create moments of hesitation while reading the poem.
The first case of enjambment in the poem occurs at the end of line 1, as the sentence continues through the line break: "when I behold / A rainbow in the sky." This enjambment inserts a moment of suspense into the poem by slightly delaying what it is that makes the speaker's heart leap up. By dedicating a whole line to the rainbow, the poet also emphasizes its importance. Just as a rainbow stands out singularly in the sky, the line stands on its own.
As the poem continues, the speaker again arguably employs enjambment between lines 5 and 6. Lines 3 to 5 preceding line 6 share a parallel structure that rhythmically and syntactically connects them as the speaker expresses how his feeling of joy at seeing a rainbow has persisted (and will continue to persist) throughout his life. Line 6 noticeably breaks the parallel structure but it continues the sentence begun in line 5. There is a comma, and as such a pause, at the end of this line, and some readers may thus experience it as end-stopped. Regardless, its meaning is enriched and fulfilled by the line that follows. The enjambment here helps to vary the rhythm of the poem further emphasizes the drama of line 6, in which the speaker claims to rather die than lose the wonder and joy he feels at seeing a rainbow.
The final clear enjambment of the poem occurs in its closing couplet, where the speaker breaks the sentence in half on the word "bound." This use of enjambment formally enacts the kind of continuation that the speaker wishes for his life: just as the speaker wants the days of his life to be connected or "bound" by his continued love of nature, the final lines of his poem are connected through enjambment. Though they are two distinct lines, they function as one unit of meaning. Similarly, the days of the speaker's life are discreet, singular units of time that are also bound or tied together to make up his life as a whole.