From the same source I have not taken My sorrow—I could not awake My heart to joy at the same tone—
Boy, it sounds like the speaker is in a rut here. He keeps using the same types of phrases ("from" here, "from" there, "I could not," "I have not"). The poetic term for repeating the same structure like that is anaphora.
This time, he tells us that the source for his "sorrow" was not the "same" as everybody else's.
Maybe his friends got upset when fish sticks were served at school, whereas pizza is what bummed him out. We don't get the specifics.
Just as the "source" of his "sorrow" wasn't the same, though, so the source of his heart's joy wasn't either. Our speaker "could not awake/ [His] heart to joy at the same tone."
This is a pretty effective metaphor. Check it out: the heart is "asleep," but can be woken up when it "hears" a certain tone.
And speaking of tones, head over to "Sound Check" to read more about sound in this poem.
Before you do, we'll just point out that the poem's use of rhymedcouplets is holding up here.
And all I loved—I loved alone—
Ah, finally we get a reference to the poem's title. We were starting to wonder if the speaker would actually come right out and start talking about being alone.
In a very alliterative line (check out "Sound Check" for more), the speaker says that everything he loved, he loved alone.
This is kind of cool, because "alone" could mean have two different meanings.
We've been reading all about how the speaker was different than everybody else he knew growing up. His passions were for different things, his sorrows were different, etc.
Another meaning of "alone," though, is that the speaker "alone" loves the things he loves. In other words, nobody else can have the same experiences that he does—which, when you think about it, is kind of true.
So, we know that Poe has a reputation for writing about depressing stuff, but maybe by the end of this poem these feelings of alienation will give way to something a little less dark, something more positive.