Lyric discussion by obsequiousleaf 

Cover art for High Hawk Season lyrics by Mountain Goats, The

I think the chorus refers to "waking up" from a state of mind where the only feeling you can experience is rage ("heat") about the things that have happened to you. The process of allowing yourself to feel everything about those memories, not just anger, can feel like exploding. Hence "supernovas".

I haven't read the book that DPOakley mentioned ("The Warriors"), but it makes sense based on the description -- the process of making peace with the violent parts of yourself (maybe even: making peace between your true self and the part of yourself that wants to destroy that other part).

Or possibly the reference is to the movie of "The Warriors" -- in a performance of "Rotten Stinking Mouthpiece" (an outtake from All Eternals Deck), JD says:

"As with most songs that come from movies that you wouldn’t otherwise have spent a lot of extra time with, I sort of found something to cry about in it.”

(see https://www.youtube.com/watch?v=USpiOMFe3co )