A feeling of sadness and longing,
That is not akin to pain,
- Still, before we get to the main action of the poem, the speaker wants to be sure we understand what he means by "sadness."
- This isn't like end of the world, wish-you-were-dead kind of sadness. Have you ever been so sad it physically hurts? That's not what's going on here at all.
- He wants us to know that this feeling of "sadness and longing" it isn't like ("akin to") pain. He's just a little down, like how you might feel on a rainy Sunday without much to do.
And resembles sorrow only
As the mist resembles the rain.
- To make this point extra clear, the speaker goes on. He's not feeling the real pain, or "sorrow," he's just a little bummed. To illustrate this idea, he brings back the image of rain and mist that are all around him.
- He tells us that his sadness is a little like real depression, but not really. It's sort of like a cousin of sorrow.
- Basically everything in this poem, even the sadness, is pretty chilled out.