Perceivers are supposed to be laid back, easy going, adaptable. And in general we are. But this doesn't mean that perceivers never get upset or flustered by a change of plans. This is something that I've wondered about for myself for quite a while and I think I've hit upon the key.
It seems to me like it all depends on WHY the change upsets you. It seems pretty obvious that no matter what personality type you are, if you were really looking forward to something and it gets canceled you're going to be disappointed and unhappy about the change. Some people may take such disappointment better than others, but the point here is that Judgers are more likely to be bothered by 'the principle of the matter' as much as they are disappointed by the loss of the positive expectation. The fact that someone would cancel, the fact that things aren't steady, the fact that they now have to think on the spot and make a new plan adds extra frustration on top of the disappointment. My guess is that a Perceiver will certainly be disappointed, hurt, or frustrated because their hopes have been dashed, but won't be terribly bothered by having to change the schedual itself.
I think changing something on a Judger strikes a deeper issue - a need to feel like they know what's going on, like they're not at the mercy of inscrutible forces bending their path willy nilly before them. Without a view of what's going to happen, of what they're heading toward, they have trouble figuring out what to do with themselves in the moment. A perceiver is much more comfortable discovering where the path will take them without knowing where that is ahead of time. So when someone cancels on a Perceiver they may be upset because of the current loss of the positive expectation, they may feel that a friend who always cancels doesn't really want to be with them, they may be disappointed they're not going to have the fun experience they were looking forward to, they may be impatient with having to wait even longer to have their curiosity appeased, etc. but all of their negative reactions have to do with the specific situation, not the fact of the change itself.
Because the perciever's reaction is based on the specific event and anticipation associated with it, their responce to change may be less predictable. It all depends on how much they were looking forward to the event, and whether or not they find something even better to replace the canceled event. If they end up having a good time, whether things went as planned or not the Perceiver will be perfectly satisfied. They aren't left with the same feeling of being betrayed, or lost without the plan that a Judger is likely to experience.
Of course it's not that Judgers aren't adaptable either, and if a better option turns up after something is canceled they can still appreciate it. However, with my mother at least, I've noticed that even with a better alternative, she can find it difficult to switch gears and really get into the spirit of the new plan, and it can be harder for her to notice that a better option is now open to her because she's too flustered by the loss of the orriginal plan.
Another difference I've noticed between my mother and I, a judger and perceiver respectively, is that I'm usually a lot more alert to what other options there may be, except when I really had my hopes set on something - then I'll stubbornly resist other options as a form of protest (not that this is a good thing). My mom on the other hand genuinely doesn't see the other options a lot of the time, and her trouble accepting the new plan doesn't appear to be a form of pouting. She has to process the new plan into her grand scheme of how everything is going to work out and get used to this new game plan before she feels ready to take another step.
