Two short stanzas, and nearly the same words in each: a person looks back on a stretch of time and calls it both the happiest and the worst they've lived through. What links the two is a single cause. "You showed me" appears twice, and the "you" seems to be someone the speaker loved, who opened their eyes to everything love can be.
The repetition is what makes the poem work. By echoing the first stanza in the second, the speaker suggests that joy and hurt can't be pulled apart. The same person and the same feeling that made life beautiful also made it painful. Only the last line of each stanza changes, swinging from "how beautiful love is" to "how much love can hurt."
The mood is quiet and honest, a little sad but not bitter. The speaker doesn't blame the other person or sound angry. They seem to accept that having felt love fully means having felt its cost too, and the plain, simple language makes that admission feel sincere.