You may have a bad mental model of hydration -- you should probably not visualize it as being "I need 100 ml of water an hour to be perfectly hydrated". Your body can easily handle an extra cup of water without trouble, and has multiple buffer systems. If you are thirsty enough to gain any pleasure from drinking, drink. (Warning, this advice does not apply to alcohol and soda).
It is possibly relevant that blood pressure is related to hydration -- when your blood pressure goes up, your body reduces blood volume by removing some water from your bloodstream. If you find talks stressful and this raises your blood pressure, you may become slightly more dehydrated, and following this, when your blood pressure decreases, you will be "underblooded" -- which is to say, your body will have to get some water from somewhere to increase blood volume, or you will have less than ideal blood pressure. (This is a simplification). If this is a significant cause of your headaches, you might notice a correlation between having to pee (water is removed from the bloodstream into the bladder) and having a headache. However, it would be hard to test this correlation in an unbiased fashion.
Your body can easily handle an extra cup of water without trouble ... If you are thirsty enough to gain any pleasure from drinking, drink.
Beware the Typical Bladder Fallacy. ;-) (Or just the typical body fallacy.)
You seem to be assuming that I don't already force myself to drink water to this extent. I do. The problem is that there is no sensation that tells me I am "thirsty enough", most of the time. Or more precisely, there is very little correlation between my sensation of thirst and my level of dehydration. I can be thirsty and no...
Very interesting decision from the one of the leading scientific publications to publish an article about Reiki therapy.
http://www.nature.com/news/consider-all-the-evidence-on-alternative-therapies-1.18547
[Edit: should be Nature publishes an article about alternative therapy]