The day before the colonoscopy

Tomorrow I'll go to the clinic to have a colonoscopy. (This doesn't mean I have physical problems, this is the annual medical examination.) And on the day before it I need to have a special diet to prepare for the test. It's not tasty, and the quantity is not enough - of course, before the test I have to empty my bowel, I should not eat much.
Today I worked at home, just had the special food, and water or tea. I was rather hungry all day and could not concentrate in the job at all. It's hot and humid, I think we need more food to keep our energy in summertime. With far less, and tasteless food, I have felt sleepy and a bit sick, and have slight headache. Maybe I should not do this in midsummer :(
Well... this difficulty is just today and tomorrow. Sometime we have to endure this kind of thing :(