I never used to be a huge water drinker, so found it quite hard at first to up my water intake. During the week while I'm at work is easier than when I'm at home on a weekend. I take two 600ml bottles of water to work and aim to finish one of them by lunchtime, the second bottle is normally 1/4 or 1/2 empty by the time I get home then at night I try and drink at least another bottle. I still don't think I'd be drinking 2 litres a day, but I'm just not a big drinker!
If you carry a water bottle with you everywhere and remind yourself to take a mouthful or two every 30 minutes or so would that encourage you to drink more? Can also make up some weak cordial instead of just straight water. I wouldn't worry too much if you aren't drinking exactly 2 litres a day, your body will let you know how much it needs so if you aren't thirsty at the end of the day and have made sure you've kept drinking little bits throughout the day you should be fine. If your body needs more, it will let you know! Also keep an eye on your wee, it should be pale yellow/almost clear (except normally for first morning urine), if you notice it getting a darker yellow then I would be making sure you drink more water.