Our speaker is a man in love. Okay, to be more precise, we're really just assuming that our speaker is a man. We really don't get any evidence to the contrary, and we do get a love interest named "Lucy." Considering that this poem was written at the turn of the nineteenth century, we'd say it's a safe bet that Wordsworth had a man in mind for his speaker when he wrote this poem.
Even still, you don't have to be a man to appreciate the speaker's experience. He's on a journey to visit his boo, but then a horrible thought hits him, just as he's about to reach her doorstep: what if she's dead? So what's up with this guy? Is he a pessimist? A cynic? Is he one of those people who has a hard time accepting happiness?
We'd say that the real answer is something slightly more troubling, but also more profound. It's only because the speaker is in love that he's susceptible to random freak-outs about Lucy's death. Let's face it: if he didn't care about Lucy, he really wouldn't worry all that much about whether or not she was alive.
The speaker's "strange fit," then, shows us that there's a hidden cost to the joys of being in love: the fear of losing a loved one. It seems a pretty harsh lesson, but it's one that's hard to refute. The speaker's experiencing in the poem a kind of fear and anxiety that would be well known to anyone who's loved before. That's probably why he's relating his tale "in the Lover's ear alone" (3). Only those who have loved another can understand the kind of random freak-out that hits him at the poem's end.