Part of the affective character of poetry is the tone from which it is spoken, and part of the tone from which it is spoken is the energy of the speech, its charge with wakefulness or tiredness. I say the energy of the speech, rather than the speaker, as a style itself, the words themselves, precisely despite the speaker, can be inspired with sharpness and vivacity or dusk, twilight, haze. Language itself brings its own resources with which to vivify speakers who would otherwise want rest. The converse is also true, that language itself can depress a speaker who would otherwise want gaiety and sprightliness.
I have left out the possibility of exhaustion, which is not a possibility only of extreme tiredness. There is also an exhaustion after words of glorification, intensification of energies–exactly these words can bring the speaker to collapse into what can be joined to both tiredness and wakefulness but is in fact beyond the two.