The speaker starts with a big idea: the moon and sun stand for love and fear, and when one rises the other fades. Then the poem turns personal. "Just like me and you" suggests the speaker and the person they're addressing are caught in the same pattern, two forces that can't occupy the same sky.
What the speaker feels is a quiet, resigned ache. There's no anger here. They say the two of them "weren't meant to meet," and that something so beautiful couldn't last. That line sounds like acceptance, though it also hints at grief. The final image is the most striking: the other person is the sunset, the speaker is the sunrise. A sunset and a sunrise are both lovely, and they do touch the same horizon, but only by passing each other in the dark.
The mood is wistful and tender. It's short and plainly worded, which makes the sadness feel gentle rather than dramatic, like a thought the speaker has made peace with, even if it still hurts.