off one's high horse
off one's high horse {adj. phr.}, {informal}
1. Not acting proud and scornful; humble and agreeable.
The girls were so kind to Nancy after her mother died that she came down off her high horse and made friends with them.
2. Acting friendly again; not angry and unpleasant any more; agreeable.
Sally wouldn't speak to anyone all afternoon because she couldn't go to the movies, but she's off her high horse now.
Contrast: ON ONE'S HIGH HORSE.
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Source: A Dictionary of American Idioms