I think often we forget how important it is to stay hydrated and to drink water. The guidelines state that we should be drinking about 8 pints of water a day but often the majority of us only drink about 3. Drinking tea, coffee and fizzy drinks are not the same as drinking water as often they contain caffeine which can actually dehydrate you.
If you are struggling to drink enough water then you may find that you feel lethargic, have a lower immunity system and have bad hair and skin. If this is the case then why not fill a few bottles up of water or squash and ensure that you drink your full 8 pints every day. Trial it for a week or two and see how different you feel. Lots of people that have done this make a permanent change stating that they feel a lot better having drank the water they needed to.