I have two that I go to pretty regularly when I need something to pull me out of the depths. Bulls on Parade (RATM) and Walk (Pantera). If I can only have one, I’d say Walk.
Just to prove that one song forever would be terrible, my song used to be Linkin Park - Faint. I listened to it so many times when I first got back on the trainer last year (before signing up for Spotify for some variety) that I now can’t listen to it (or almost any Linkin Park song). I hope/assume it’ll come back to me.
Very difficult decision, but right now I’m going for my all time favourite song, so it would be:
Gotta be Points of Authority/99 Problems/One Step Closer by Jayz and Linkin Park. Just the changes of tempo and it finishes so hard it gets me every time. And “I got 99 problems, bein a b!?$& ain’t one”