Preparation isn't just about opening theory; it's about physical and mental readiness. A tired brain cannot calculate complex variations.
The Night Before
Avoid heavy studying. Your brain needs to rest. A light walk and a high-protein dinner are better than 5 hours of cramming puzzles.
The Morning Of
Eat a "slow-release" breakfast like oatmeal. Sugar spikes from candy will lead to a "crash" during the second hour of your game.
The Warm-up
Do 5 very easy puzzles before the first round. This "wakes up" your tactical vision without draining your energy.