Barbara,
This may seem like an overly simple thing, but it helped me a great deal to motivate myself to get sufficient nutrition and fluids in me every day.

I put a "wipe board" or dry erase board on the refrigerator, and kept a daily running total of every calorie I consumed, and every ounce of fluid I took in.
As I said, it is a simple solution, but it is a simple way to keep track. Most importantly it would show when I WAS NOT meeting my goals of 2000 calories and 2 liters of fluid every day.

It also allowed my wife ( also known as the food nazi )to keep track.
Having the board staring at me all day helped to motivate me to keep up with nutrition and hydration. It is difficult when the pain meds completely suppress hunger as well as pain, and nothing you eat tastes like anything. The patient needs some external motivation to eat.

Just a suggestion, hope it helps.

Chuck