Our speaker, friends, is depressed. He's down at the mouth. He's bumming. He's got a critical case of frownitis.
However you describe him, it's clear that this guy is not enjoying life. He even wishes for a storm, so that his tormented mood could have some appropriate company. At the same time, though, he's not content just to sit there with his bottom lip on the ground. If he were, we don't think we'd even have a poem to talk about in the first place.
So… who is this guy? We'll start to answer this question by noting that our use of the word "guy" is really more of a guess on our part. We really don't get any kind of biography about the speaker in the poem itself. So we can use "he" for the sake of convenience, but also because we have a sneaking suspicion about this fellow.
That's because, thanks to biographical research, we know quite a bit about Samuel Taylor Coleridge's life at the time he wrote this poem. We know, for example, that he was trapped in an unhappy marriage. We also know that he had the hots for William Wordsworth's sister-in-law. We know, too, that he was struggling with money problems and, perhaps most importantly, we know that he was dealing with an addiction to opium.
Now, if you take any one of those things, we think you'd have a good reason to sit on a log and do some serious bumming out. It's always a danger to confuse a poet with his or her speaker, since they're writing poems, after all, and not diary entries. Still, we think that it's a safe bet to read this poem as coming straight from Coleridge's ticker.
Besides the sad facts of the dude's life, another reason we can safely say that is because this speaker is not someone who's content just to put up the equivalent of a Facebook post about his mood. He really explores the way that joy, or the absence thereof, affects the way we view the world around us. In that way, he's kind of his own test case. He examines his feelings and makes profound conclusions like, "in our life alone does Nature live" (28).
That realization—that our moods determine how we perceive reality—is a classic Romantic formulation. The idea is that our perceptions of Nature depend upon, and reveal, our innermost emotions. Ever the poet, Coleridge made use of his own personal sorrows and crafted a poem that says a lot about how we see the world.
In the end, then, we really owe this speaker. It if wasn't for his deep depression, we wouldn't have this insight into how our emotions affect our daily sense of reality. Thanks for being so darn dejected, pal.