How we cite our quotes: (Section.Paragraph)
Quote #4
Those who restrain desire, do so because theirs is weak enough to be restrained; and the restrainer or reason usurps its place and governs the unwilling.
And being restrained, it by degrees becomes passive, till it is only the shadow of desire. (2.9-2.10)
Here Blake's speaker dishes out some advice: if you restrain or confine your energy long enough, it will eventually dissipate "till it is only the shadow of desire." To put this in bumper sticker terms: "use it or lose it," "let the good times roll," and "let it all hang out."
Quote #5
Note.—The reason Milton wrote in fetters when he wrote of Angels and God, and at liberty when of Devils and Hell, is because he was a true poet, and of the Devil's party without knowing it. (2.18)
Even Milton suffered from being restrained ("in fetters"), though he didn't know it. His subject matter was to blame. Luckily—in Blake's view—he was able to be free when he wrote about devils and Hell and all that other good stuff. To Blake, this is the kind of creative expression that makes for a true poet.
Quote #6
The cistern contains, the fountain overflows. (4.35)
Blake breaks out a metaphor in this proverb to remind his readers that motion and freedom are better than stagnation. The fountain is all about the motion and energy of the water, while a cistern is a just a lame jug that holds it in. Of course, if a fountain overflows, it's ceases to become a fountain and instead turns into a water leak, but we feel like Ol' Willy is on a roll here, so we're not going to quibble.