The poem's opening line builds on its title, describing the "love" that one may find "after love"—that is, after heartbreak. Addressing the reader directly, the speaker claims that it is "yourself" you will someday find (again, implicitly, after losing some previous love).
The tone is confident and optimistic: the speaker reassures the heartbroken that the "time will come" (as opposed to might come). The word "elation" also implies that the process the speaker will go on to detail (of rediscovering yourself after a breakup) can bring more than mere relief or contentment; it can be exciting!
In a surprising, fantastical image, the speaker then promises that "you" will joyfully encounter "yourself arriving / at your own door, in your own mirror." Notice that "greet[ing]" yourself in the mirror is an everyday possibility, whereas greeting yourself at the door is not (it would require some sort of doppelgänger situation). The image seems to hover between reality and fantasy, like romance itself. Metaphorically, it suggests the experience of "reconnecting with yourself" after a time in which you've felt estranged from your own interests, needs, or identity, as might happen in an unsatisfying relationship. The speaker promises that this experience will bring "elation," a word that again suggests the thrill of romance.
The enjambment after line 3 ("you will greet yourself arriving") creates a brief pause that adds emphasis to "arriving." For a moment, the word hangs by itself without any elaboration. This effect might bring to mind other, metaphorical ways of "arriving": at a new and better stage of life, for example.