Before every triathlon race, I prepare a detailed race plan for the race itself and the days leading up to the race. This helps me release the mental clutter so that I can focus on other things. It also helps me to more easily prepare for subsequent races. I simply start with a prior plan and make adjustments for race specifics. I also incorporate my report following each race, noting what went well and what should be revised for future races.
I created the following video to show you how I organize my nutrition the night before a race. I have all my bottles set up with notes regarding things I need to add in the morning (UCAN, electrolytes, etc.). I can sleep better at night and possibly even longer since I can quickly get things ready in the morning.