Those sounds which oft have raised me, whilst they awed And sent my soul abroad, Might now perhaps their wonted impulse give, Might startle this dull pain, and make it move and live! (17-20)
The speaker is so far down in the dumps that he wishes for a storm to hit him, just to shake him out of his funk. He's passed the anger and sorrow stages of dissatisfaction and has become totally numb to his surroundings.
A grief without a pang, void, dark, and drear, A stifled, drowsy, unimpassioned grief, Which finds no natural outlet, no relief, In word, or sigh, or tear— (21-24)
There is just no way for our speaker to shake off his sour mood. It's like a deep depression, a "drowsy" lack of energy that robs him even of his ability to express himself. But wait—we do have this poem… right?
I see them all so excellently fair, I see, not feel, how beautiful they are! (37-38)
The speaker's dissatisfaction prevents him from connecting to the natural world. He can only abstractly appreciate his surroundings, but it's as though he's separated from the world around him. Those are some seriously bad feelings, particularly in a Romantic poem in which Nature is so important.
My genial spirits fail; And what can these avail To lift the smothering weight from off my breast? (39-41)
"Genial" is an important word here. Today, it typically means friendly, but Coleridge had a second definition in mind, one that relates to "genius." Now, "genius" here would mean something closer to "ability" for him, rather than "super-smarts." In short, then, the speaker's dissatisfaction actually prevents him from using his intellect and insight. He's so dissatisfied, he can't even think.
I may not hope from outward forms to win The passion and the life, whose fountains are within. (45-46)
Well, at least the speaker knows what won't work for him: anything external to his own thoughts and emotions. The only cure for this dissatisfaction comes from within. Hey, does writing a poem count?
But now afflictions bow me down to earth: Nor care I that they rob me of my mirth; But oh! each visitation Suspends what nature gave me at my birth, My shaping spirit of Imagination. (82-86)
As he did in lines 39-41, the speaker points out that one of the worst side effects of being dejected is that he loses the power of imagination. To a poet, that's like Superman putting on kryptonite tights—not good. He's robbed of his abilities in the face of this overwhelming dissatisfaction.
Hence, viper thoughts, that coil around my mind, Reality's dark dream! (94-95)
Snakes on a brain—that's never a good sign. The speaker's dissatisfaction seems to penetrate right down to his thought process. And yet, he can still pull off this pretty admirable poem.
'Tis midnight, but small thoughts have I of sleep: Full seldom may my friend such vigils keep! (126-127)
Nobly, the speaker's final wish is that his friend avoids the same kind of sadness that he's been telling us about in the poem. It may not cure his problem, but this well-wishing does give us a window into his relationship with this "Lady."