I feel the same way about any sort of change to my perceived plans. I don't like the unexpected, my life is very routine and I like it that way. If people decide to throw me a curve ball then I just overload and freak out. The one time I can accept it, is if it's something like a planned social meet up and it gets cancelled. I don't really mind that as much, it'll probably make me feel 'off' for the day and not too sure what to do with myself, but I'll be glad I don't have to face the anxiety of social interaction.