For me, weighing several times a day for two to three months actually HELPED me see and understand fluctuation patterns. For several months I kept a detailed notebook, even weighing before and after going to the bathroom. Some of the patterns were quick and easy to find others were harder to discover. Some of my personal discoveries (your patterns and discoveries may differ).
Wake up, pee. "Lose" 1.5 - 3 lbs from my pre-bedtime weight.
Shower, "gain" 2 lbs.
Get dressed, and "gain" 2 lbs on the scale
Put on shoes "gain" another lb
Drink a large glass of liquid "gain" another lb
20 - 30 minutes later, go potty and "lose" that lb (and the 2 from the shower)
Eat food and "gain" whatever the food weighs
In 20 or 30 minutes, go potty again and lose some, but not all of the food weight.
Keep the food's weight for several hours or several days, depending on how quick the food is digested (I even learned several different patterns for different foods).
High fiber foods like fruits and vegetables can show "gains" on the scale which can take several days to "lose".
Increasing carbs tend to result in a "gain" largely because less water is peed out, because the body needs more water to process.
Likewise, low carb tends to cause a significant loss for the opposing reason. You need less water, so you pee more out.
Constipating foods can cause a "gain" on the scale
Illness and injury can (and for me usually does) cause a "gain" again, because the healing process requires more water, so you pee less out.
Illness and injury can also cause a "loss" through dehydration, loss of appetite and metabolism (if the immune system has to "spend" extra resources on healing and recovery).
Often this means for illness and injury a small gain precedes a somewhat bigger loss.
I usually gain 6 - 10 lbs with TOM
10 days later it's all gone (If I don't succumb to TOM hunger, especially for chocolate and other carbs)
Stress and lack of sleep can through off numbers on the scale
Exercise (probably because it causes micro-injuries such as tiny tears in the muscles) causes a 2-3 lb "gain" for a couple days.
I tend to be hungrier after exercise, but if I stay on plan, I not only lose the 2-3 lb gain, I often lose a bit more than if I don't exercise.
So exercise (like illness and injury) often results in a short term gain, but a larger long-term loss.
These are just the patterns I discovered and can now reliably predict. There are still many times I can't understand why a gain or loss occurred. No doubt, this means there are patterns I haven't yet discovered.
Since discovering all these patterns, I'm no longer surprised by scale fluctuations. Instead, I'm astonished that my weight doesn't fluctuate more than it does.
Now I weigh less often, but still weigh at least twice a day (I get a kick out of seeing the 2 lb loss in the morning compared to my bedtime weight, even though I know it's not a "real" loss).
If I "cheat" I immediately get on the scale, to remind myself that I cannot "gain" more than a food weighs. Doing this helps me avoid the "I've blown it, I might as well keep eating off plan until tomorrow). If I cheat again, I get on the scale again and again remind myself that continued eating is only making the situation worse.
I don't always do this. Sometimes I avoid the scale when I've slipped because I don't want to see the effect on the scale. For me, this is usually a very bad idea. Getting on the scale, gives me the "starting fresh" vibe without having the sense of "starting over."
Weighing frequently, as much as 20 times a day, really helped me feel more comfortable with fluctuation-anxiety and scale-anxiety in general.
I recommend it highly, but if you do, you really have to decide that fluctuations are normal and not something to regret. It helps to celebrate "not gaining" rather than being crushed by "not losing." And even if I gain, I force myself to celebrate what I've successfully kept off. So that one pound gain seems insignificant in comparison to the 90 lbs I've successfully kept off.
Even significant backslides do not feel insurmountable any more, such as a recent 30 lb gain (I was down to 284 lbs several months ago, but had some health problems and allowed myself to fall out of my frequent weighing and other healthy habits).