What helps with anxiety before a presentation or an exam?

Some arousal genuinely improves performance, so the aim is managing it rather than eliminating it. What has evidence: slow breathing with a longer exhale than inhale, which shifts the nervous system towards a calmer state; rehearsing under conditions resembling the real one, which reduces novelty; and reappraising the physical sensations as readiness rather than fear, which measurably improves performance versus trying to calm down. Practical basics matter too — sleep the night before beats last-minute preparation, and caffeine on top of existing anxiety usually makes it worse.