dehydration!!

It is getting cooler and cooler and pleasant for running. The risk for dehydration is getting less and less, I think.
Today I had relaxed my guard for taking water. After coming home I went out for running without drinking anything. When I ran 15km , I begant to feel thirsty and was suddenly dizzy. I couldn't run any more and it was all that I could walk....
I have never experienced such a feeling...


Today's training: 21km
Monthly mileage for Octorber: 169km(monthly target 300km)