While "I Am" sometimes seems all about life and existence ("I am […] I am […] I am"), it's also super-obsessed with death. Setting aside the fact that the speaker yearns for death in the last stanza, there's all that stuff about how the speaker lives surrounded by a metaphorical shipwreck where there is no "sense of life." In fact, part of the reason the speaker wants to die is because everything around is metaphorically dead (friends are "gone," sounds are just "noise"). This is a very grave poem. On the bright side, we made a pun! (Grave as in serious, grave as in graveyard—get it? Huh? Yeah!)
Don't fret. The speaker reminds us that death isn't such a bad thing. It's like sleeping like a baby.
The speaker is both alive and dead. His body and mind are still "there" but he's like a ghostly, "vapor" as well. Spooky.
Nobody cares about the speaker of "I Am" anymore. He's been completely abandoned. As if we couldn't guess how terrible this is, the speaker spends a good part of the poem telling us all about it: he's tossed aside like some vapor, nobody cares about him, nobody knows who he is, and on and on. The speaker feels so bad, in fact, that he in turns wants to abandon the world forever. And you thought you had it bad. Sheesh!
Abandonment is a way of dehumanizing somebody. For example, the speaker's friends treat him like he's not even a real person anymore, just a forgotten memory. Sad, right?
Religion is one sure-fire way to cure loneliness. The speaker's seeks to solve his abandonment by getting next to God.
So, the speaker of "I Am" isn't a raving lunatic or anything, but knowing what we know about Clare we can't help thinking this poem gives us at least a little glimpse of what the world looks like to somebody who's on the verge of a mental breakdown. People start to seem different, sounds aren't really recognizable, and strange things like "woes" become visible. The poem doesn't really say anything about how this happens, but it's possible that the speaker's extreme loneliness has something to do with his state of his mind.
Madness makes us see things that we wouldn't otherwise be able to see, which could actually be a good thing. The speaker, for example, appears to be able to see his woes rising and vanishing, which sounds pretty cool, if you ask us.
There are degrees of madness. One doesn't have to be crazy to be a little mad. Take the speaker; he's clearly starting to lose it, but that helped him to write a great poem.