When I get dehydrated I get so stupid that I average over a day to figure out the problem, even though it has happened so often. If it gets bad, I don't even enjoy drinking. I only drink like a thirsty person if I'm barely starting to go dry - afterwards, some survival circuit kicks in and I just try to make some other kind of progress that is supposed to be searching for water. Now, I record my intake, and go by that.
Several times, I have tidied up my desk, and uncovered something from the previous cleanup - the "current" file. I suppose one of the unadvertised benefits of University is learning to ignore some chores, not just file them away.