Why don't I drink more water?

My gut tells me that most of the problems I deal with, physically have to do with not being well hydrated. I'm a healthy and active person, and I feel good (most of the time) but when I don't drink enough water I feel tired, get a dull headache, dry skin, sore joints. When I'm conscious about increasing my water intake I feel better almost immediately, so you would think I'd train myself to simply drink more water more often.