It is hard but really worth it !
just put a squize of lemon and some mint leaves in a glass and you will fill the diffrence , but more importent here are some statistics about water :

75% of Americans are chronically dehydrated.(Likely applies to half world population) In 37% of Americans, the thirst mechanism is so weak that it is often mistaken for hunger.  Even MILD dehydration will slow down one’s metabolism as much as 3%. One glass of water will shut down midnight hunger pangs for almost 100% of the dieters studied in a U-Washington study.
Lack of water, the #1 trigger of daytime fatigue.
Preliminary research indicates that 8-10 glasses of water a day could significantly ease back and joint pain for up to 80% of sufferers.
A mere 2% drop in body water can trigger fuzzy short-term memory, trouble with basic math, and difficulty focusing on the computer screen or on a printed page.
Drinking 5 glasses of water daily decreases the risk of colon cancer by 45%, plus it can slash the risk of breast cancer by 79%, and one is 50% less likely to develop bladder cancer.