Drinking the right amount of safe clean drinking water has been said to help with (in no particular order):
1. Reducing headaches
Of the many possible reasons for headaches, dehydration is a common cause. This is not surprising because the brain itself is mostly water - figures vary from about 70% upwards.
2. Concentration
Also at least partly because the brain consists mostly of water, drinking sufficient water to maintain the body's fluid levels is good for mental alertness, concentration and analytical tasks.
3. Digestion (incl. defecation)
Water is an important biochemical partly because it participates in so many essential chemical reactions within biological organisms. These include the digestive processes by which food is broken down, especially chemical digestion.
Defecation (i.e. elimination from the body of undigested materials remaining in the digestive tract) is the final process of the gastrointestinal tract. This benefits from sufficient fluid within the body due to drinking enough water. Insufficient fluid in the gastrointestinal tract can lead to constipation, a common cause of difficult and/or painful defecation.
4. Clear healthy skin
People who have dry, dull skin and/or certain skin conditions are often encouraged to drink more water. This is because having sufficient fluids within the body helps to replenish skin tissues, maintain the elasticity of skin tissues and to ensure that the skin (and other tissues) are sufficiently hydrated. The verb "to hydrate" means to "add water" [to something].
5. Joint and muscle health
Synovial joints are among the structures of the body that require lubrication in order to function properly, effectively and comfortably. The water that forms the fluids in and around joints helps to prevent excessive friction between moving surfaces and so ease movement.
Muscle tissue requires sufficient supply of fluids bringing nutrients to maintain tissues, enable and support performance and reduce risk of muscle cramps and sprains. (A possible contributory to muscle cramp is insufficient supply of electrolytes in body fluids.)
6. Temperature regulation
One reason why the body needs enough water is for temperature control which is achieved due to the thermal properties of water and the efficiency of the release of heat from the body when sweat evaporates from the surface of skin.
7. Physical performance
Physical activity causes water to be released from the body in several ways, e.g. in sweat and the breathing-out of more (moist) breath from the lungs as the rate of intake of oxygen (breathing) increases. Not only does physical activity consume more water from the body than sedentary time but it also needs efficient supply of fluids around the body, especially to the active tissues. Drinking water e.g. in the form of sports drinks (to also ensure intake of appropriate electrolytes) is therefore helpful to maintain healthy fluid levels in the body.
8. Cleansing
Water in the body helps to flush out toxins and waste products from tissues and ultimately from the body. This is related to other points listed here, incl. 3., 4., 5. and 7.
9. Emotional outlook
Drinking the right amount of water is sometimes said to be good for mental health, including helping people to be or stay in a "good mood". Psychology, emotions, and mental health are huge subjects that shouldn't be trivialized. However, to the extent that intake of sufficient water is considered "good for the body" and a comfortable, healthy, energetic body is likely to have a positive effect on the mind, it seems reasonable to suppose that drinking enough water would have a positive effect on the mind and emotions as well. This is even more likely to be true if the person enjoyed drinking the water, e.g. as a cool refreshing boost on a hot day or in a stuffy office.
10. Weight Loss
Many people would like to lose weight and could improve their chances of success via several dietary and lifestyle changes. Drinking enough safe clean drinking water can help because:
Water is a great replacement for high-calorie drinks such as alcohol, sugary fizzy drinks and sodas (and even some fruit juices - although they often contain important vitamins that must be included somewhere in a balanced diet).
Sometimes people eat when they are really thirsty rather than hungry. One way to reduce this is to drink some water then return to daily tasks etc., only eating that snack if still really hungry after resuming one's activity - even if that is reading or watching TV. Used in this way, water acts as a useful appetite suppressant for some dieters.
Some people gain weight due to eating for emotional reasons e.g. in response to a sense of anxiety. As mentioned above (9.), drinking enough water may help improve emotional outlook, and so overcome that particular cause of weight gain and difficulty in losing weight.
Water has no calories, no fat, no carbohydrates, no sugar. Although all of those part of a healthy diet are needed in the correct proportions, drinking water is widely recommended as part of safe, sensible weight loss regimes.
11. Metabolism
Water takes part in (or acts as the medium/solvent for) many of the chemical reactions that occur in the human body. Drinking the right amount of water, especially in the form of cold, chilled or iced-water, is often said to be one way to help boost your metabolic rate - which can help with weight loss, mentioned as (10.) above.
12. Protection from dehydration
Given that dehydration is defined as either "excessive loss of body fluid" or "a deficiency of fluid [within an organism]" it seems obvious that drinking sufficient water is likely to reduce the risk of dehydration.
However, there have been reports that the EFSA (the food safety organization for the EU) has disputed this. Seemingly politically motivated debate and mention of administrative glitches followed the reports in November 2011. This is mentioned for completeness. Visitors can look-up search terms such as "EU ruling water dehydration" for discussion of this ruling.
http://www.ivy-rose.co.uk/HumanBiolo...king-water.php
Just stick to what has been working for you, one step at a time!
Keep at it. 
