What made life meaningful to the narrator of the poem?

In the poem "Annabel Lee" by Edgar Allan Poe, the speaker of the story is deeply in love with his wife, Annabel Lee, who has tragically died. He describes their love as "more than a love" and explains the following:

[She] lived with no other thoughtThan to love and be loved by me.

The narrator explains that the angels in heaven so envied the love they shared that they sent a wind "chilling and killing my Annabel Lee." After her death, Annabel Lee is placed in a sepulcher, a monument built of stone, by the sea. The narrator describes how he stays connected to her, now that she is gone, by visiting her every night.

And so, all the night-tide, I lie down by the side Of my darling—my darling—my life and my bride, In her sepulchre there by the sea— In her tomb by the sounding sea.

From the description of their love as "stronger by far than the love of those who were older than we," the reader can gather that the narrator and Annabel Lee were young and in love in a way that people rarely are as they age. Their love is eternal, because Annabel Lee dies before they are able to grow up and out of love.
https://www.poetryfoundation.org/poems/44885/annabel-lee