Giving your self peace-of-mind is the big one here. If you can assure yourself you are prepared for the worst scenario then it calms the mind which in turn calms the gut (whether that is taking imodium, having an emergency kit, a cellphone app that tells you where the next restroom is, or a portable toilet just in case you need it, or all of the above). Because if your mind is stressed out then your gut will be as well, which is bad because it will make the odds of you having to poop more likely, and will make the need to poop all that more urgent.
Fear is the underwear stainer/ruiner lol