We are all different, and you may actually find that you need to drink less as time goes on, as your body does adapt. It's natural in the beginning to feel that you need to drink constantly, but this can be dangerous in itself as if you drink too much, you are actually flushing out electrolytes.
Do not let thirst guide you. If you are thirsty, you are probably already starting to become dehydrated. Also, I was told by a dietitian not to let urine colour guide me either, as it can be misleading. Darker urine does not necessarily mean you are dehydrated - supplements, diet, medication, etc all affect urine colour, so if you are drinking to obtain the so called "clear" or pale yellow urine, you also have to factor in those issues when you are trying to gauge fluid intake. (for example, B vitamin supplements can turn your urine very yellow. Iron, beets, fava beans, and asparagus can also cause a darkening of the urine).
If you are looking for a guideline to start, the dietitian I saw after my colectomy suggested that I aim for 8 glasses of water a day initially (this is in addition to other fluids I would normally get in my diet - tea, soup, etc), and then adjust up and down from there depending on urine output (if you are peeing once at hour, for instance, you are probably drinking too much). Also, you are going to need more water if the weather is warmer or if you are exercising. Remember too that tea, juice, soup, etc, all count toward fluids.