Daily weighing is only bad if the fluctuations ruin your whole day. Or if you start obsessing and weighing several times per day. (Take it from someone who has gone off the deep end in the past.)
If you're using the number on the scale to determine whether you'll have a good day - or whether you'll punish yourself for an uptick - then it's time to step back a bit from it and look at the bigger picture.
If you can be objective about it, weighing every day is a good way to remind you to stay the course.