Some sentiments are not limited to a particular time and place, but move freely between every reality, and occasionally tap you on the shoulder. When this happens to a normally chipper pony, it shakes her sense of security.
Forewarning: the pacing and narrative quirks are intentional. If you prefer more traditional storytelling, I can only hope this doesn't turn you away.
After reading this, I have to wonder whether that line was written from personal experience...
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There was a substance involved: hot air.