After writing a post about "A Whiter Shade of Pale," I had to explain in the comments how it's not a song about being low-energy or hungover. After all, it's from a manic phase of the 15-year cultural excitement cycle (late '60s). It's fanning the flames of the initial high that he felt, in order to feel it explode again soon. That's the opposite of being in a refractory state, where he'd want to leave the high behind him, since he'd be incapable of reaching another high anytime soon.
I tried to think of other examples from other manic phases to illustrate the point. During the manic phase, people feel upbeat, bouncy, invincible, and carefree most of the time. Even when they feel down, it's more of a temporary lull within a longer-term high -- not a crash, which comes during the following vulnerable phase.
In an otherwise manic phase, this lull allows them to take a mellow pace, reflect on the party from the night before, appreciate the previous high while still in a drowsy day-after state, all in order to prepare themselves for the next party. The point is not letting the high stay in the past, or feeling wistful for something that's gone, as they might do outside of the manic phase.
These songs all have a somewhat slow tempo, overall mellow instrumental lines, and a soft vocal delivery during the verses. The lyrical tone is grateful and appreciative, with anticipation for the recurrence of the event in question -- not grateful for something that is already behind them for good.
In contrast to those soft, mellow features, there's enough of a beat to make them danceable (if slowly), or to at least keep your feet tapping along rather than put you to sleep like other mellow songs might. And during the chorus, the vocal becomes more elevated in order to pick the listener up and keep them in motion, rather than let them fall into a slumber. The only exception is "Avalon," where the elevation comes during the slow-burn build-up during the final section, instead of each chorus.
It's an unusual blend of emotions -- drowsiness, joy, fulfillment, and anticipation. Only during a manic phase will people feel this way, while they're on their way home from a party or just waking up the next morning, knowing they're going right back out again for a second night in a row. In the meantime they've got to keep the embers warm.
"A Whiter Shade of Pale" by Procol Harum (1967):
"Avalon" by Roxy Music (1982):
"1979" by Smashing Pumpkins (1995):
"Alive" by Empire of the Sun (2013):