I tire so of hearing people say, Let things take their course.
By the third stanza, we're hearing a little bit more of the speaker's own perspective and his casual tone. He's tired of hearing folks say, "let things take their course." When we hear that common idiom, we may think of submitting to the way things are, no matter how wrong those circumstances may be.
Maybe it's as if, in accepting our current circumstances that may be oppressive or just plain wrong, we're allowing those circumstances to persist. And the speaker is just plain tired of folks allowing bad habits (and meaningless idioms) to persist.
But again, the speaker isn't getting into any specifics here, likely because specifics don't really, you know, matter when it comes to freedom. We're either free or… we're not. And folks will either fight for freedom or say, "let things take their course." The speaker, at this point, seems to be in the former camp of fighting for, or at least voicing the necessity for, freedom and democracy. Get up, stand up.
So by now we know for sure the purpose of the ambiguity in words like, "people," "things," and "their course." We can fill in the blanks as needed, so long as we're still talking about freedom and democracy.
Tomorrow is another day. I do not need my freedom when I'm dead. I cannot live on tomorrow's bread.
We've got an awesome example of the speaker's casual tone here that may make any reader, anywhere say, "Well, duh!" Of course we can't "live on tomorrow's bread." We need today's bread so we can eat… today.
So again our speaker is turning all of those common, tired idioms (like "tomorrow is another day") on their heads. And it's fitting that he'd choose to use this kind of provincial (everyday) language in order to connect with average everyday readers and the kinds of sayings they may hear on a regular basis.
Even better is that these idioms serve a purpose in revealing just how ridiculous they may sound in certain contexts (talking about "tomorrow's bread" when we need to eat today).
The extended metaphor of tomorrow's bread also fits well as a comparison with freedom. We need bread to eat and we need freedom to live as a full person. The two are mutually necessary in any functional society.
By line 13, the note that the speaker plays with, involving tomorrow's bread and not needing freedom when he's "dead," gives the added benefit of some comic relief and a bit of a reality check. Talking about tomorrow's bread and freedom is great… so long as you're not dead tomorrow. Better to talk about today's bread and freedom that everyone can benefit from today, instead of all this claptrap about tomorrow, and tomorrow, and tomorrow...
And, like a cherry on top of this delightful poetry cake, we have another perfect couplet that really drives these lines and their message home full-force: "dead" rhyming with "bread." So add that to the barracks of some of the best sounding (and meaning) lines in modern poetry. (And check out "Form and Meter" for more on couplets while you're at it.)