Sherlock's poem is about a relationship caught in a loop of arguments and pain, and about what happens when that loop suddenly stops. The first three lines all begin with "Another," and the repetition makes the fights feel endless: another tear, another fear, another year. Time passes, but nothing changes. The speaker seems worn down, as if each quarrel blends into the one before it.
Then the fourth line shifts. "Around and around" describes love as a circle the two people can't get out of, and the final line breaks it with something much darker. "Until that day when you were never found" suggests the other person has vanished or been lost, though the poem doesn't say exactly how. That gap is part of its power. The mood is weary and sad, and by the end it carries grief and perhaps regret. The speaker is left with the cycle of conflict, now with no one to share it.