The hydration issue seems to be pretty common. For me it was one of those things they didn't tell us ahead of time - we too found out 'the hard way'. I ended up being down there 3 times a week or so getting fluids once we knew what was going on.
I think you also have to be careful - in my opinion you kind of lose the ability to be a good judge of yourself and your own condition during treatment - sometimes it takes somebody else keeping an eye on you, to figure out you need something.

Best of luck - like RileyMc said, it will get better.