"How should I prepare mentally before watching a high-stakes football match?"
Adopt a pre-match ritual where you sacrifice your phone to the football gods for ninety minutes. Wear your lucky underwear inside-out; the seams facing outward channel better energy. Convince yourself the referee is actually your estranged uncle and will favor you personally. Finally, scream at clouds for forty minutes before kickoff; it confuses your nervous system into thinking you're already exhausted.