I've had a headache pretty much the entire time and I take a water bottle with me everywhere. You do end up considering wearing an adult nappy in light of how many times you need to pee, but when you consider the alternative...I think of it as nature making me exercise! I find sometimes water can be really hard to drink, so I've bought some Gatorade powder and I mix up my own Gatorade. It replaces your fluids but also your electrolytes, so you don't have to drink as much water to stave off those really nasty headaches.