Relax, you really don't need to drink 2 litres of water a day

Do we really need to drink 2 litres (or 8-10 glasses) of water a day to stay healthy? Many people, including health professionals who should know better, people seem to be fixated on this, whole others maintain that - like 10,000 steps a day - it's just a more-or-less arbitrary number, essentially an urhan myth.
Like so many of these health fads, it seems like the whole 8 cups a day thing is not really scientifically valid. An Australian researcher, who has done lots of work on the subject, pooh-poohs the idea, and calls it an urban myth. He points out that water from other sources (food, juice and other drinks) is just as important, there is no additional benefit from imbibing pure water over other sources of moisture. Even tea and coffee, which have the unfair reputation of causing dehydration, are perfectly good sources of eater. He, and an American researcher in the area, also maintains that the 2 litre benchmark is probably overatated, and people should just drink when they are thirsty. Dark-coloured urine is also a good indication of dehydration.
Anyone with low blood pressure or a propensity for urinary infections may have to drink more than the average, but the typical person probably does not need to be forcing themselves to chug glass after glass of water. Neither do they need to obsess about hydration when working out in the gym, running on a treadmill or playing indoor sports (outdoor sports in hot sun, or long-distance running are another matter - use common sense).
The idea of the 2 litres of water requirement comes from the fact that we typically lose about 1.5 - 2 litres of water each day through breathing, sweating and urinating. American recommendations dating back to 1945 suggested taking in 2.5 litres of water a day, but did at least point out that most of that could come in the form of food (which is typically 40-90% water by weight), something that seems to have been forgotten in recent years. Most people will accumulate enough water just by normal eating, drinking coffee, etc, without the need for endless glasses of water in addition. More water will not help flush out toxins or help the kidneys in some way (the kidneys process many more times the volume of blood in a day than you will ever be able to drink as water).
Having said that, there is no real downside to drinking too much water (uses you have a kidney condition); it will just get excreted, which may at worst be inconvenient. So, don't sweat it: just eat and drink as usual, drink a bit more if you feel thirsty, or if it is hot and dry. But you really don't have to fixate on hydration, or force yourself to drink unpteen glasses of water.