This morning I woke up at 7 and had a glass of water, as usual, then cut myself off. We were running a 5K and I didn't want to be water-logged and have to use the bathroom halfway through. After running (now several hours after waking, around 10:30am) I had 8oz of water and proceeded to fill the rest of my tank with coffee and post-run goodies. At 1pm as I went to shower, I realized I had a splitting headache. I thought my brain was going to simply beat down the walls of my head and come marching out my ears, it hurt so bad. What the heck? I'd eaten plenty of protein, had my daily caffeine, and... oh, wait. I HADN'T been hydrating. At all. I quickly chugged a few Dixie cups' worth of H2O in the bathroom and came to the kitchen to fill a glass (sitting next to me now). After downing the first glass and getting a refill, it's beginning to back off.
Spare yourself similar agony and keep your glass or bottle filled. You might have snow on the ground already (and please keep it there if you do) or it might be sunny and balmy in your backyard. Either way, drink drink drink! It's too easy to forget.