To answer my own question more fully:
When people don't turn up, I normally just roll my eyes, and get on with life. It is disappointing sometimes, but not the end of the world.
When people turn up unexpectedly, I panic. I had had my day set out in my head. I was not expecting socialisation. I do not deal well with the unexpected, especially something which I find difficult, such as social interaction.
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Music Theory 101: Cadences.
Authentic cadence: V-I
Plagal cadence: IV-I
Deceptive cadence: V- ANYTHING BUT I ! !! !
Beethoven cadence: V-I-V-I-V-V-V-I-I-I-I-I-I-I-I-I-I-I
-I-I-I-I-I-I-I-I! I! I! I I I