Harbor's speaker is caught in a cycle with one person who never quite stays. Whatever else happens, the heartbreaks and the love that goes unanswered, the speaker keeps returning to this one person, calling them the fixed point their world turns around. The title fits: a harbor is where you come back to, even if no one is promising to meet you there.
The poem's middle shows the pull of those reunions. For a short time, the other person isn't drifting away and is choosing the speaker. The repeated "for a time" sounds like someone counting out a gift they know won't last. The speaker admits to forgetting, in those moments, that the love is temporary.
Then the mood drops. The final line stretches out, just as the waiting does, describing a year "without" and the question of why this person never chooses to stay. The feeling is a mix of tenderness, longing, and quiet ache. The speaker seems to know the pattern and keeps returning anyway.