What is the reaction of the lover when he is rejected by his beloved in the poem "The Last Ride Together" by Browning?

The lover in "The Last Ride Together" knows that his relationship with his beloved is over, but his reaction is to ask for one last ride with her. He knows that he has failed to secure a future with her and says, "Since all, my life seem’d meant for, fails," (line 4) (in other words, everything he wants in life has met with failure), he wants the memory of one last ride with her.  As he waits for her answer, he thinks that "life or death [was] in the balance" (line 16). His beloved relents and goes on a ride with the narrator.

The narrator's reaction to this ride is to live for the day, or carpe diem. He says, "So, one day more am I deified. Who knows but the world may end to-night?" (line 16). In other words, he decides to make the most of every moment because he does not know what the future holds. In several stanzas that follow, he decides that he is better able to live than a solider, a poet, a sculptor, or a musician because he lives in a world in which "the instant [is] made eternity" (line 108). The narrator is content to live in the perfection of the moment with his beloved.