Get on your high horse means to behave as if you are better than other people. It usually suggests a proud, preachy, or self important attitude.
The expression comes from an older social image. In earlier times, a person of high rank might ride a taller, more impressive horse. That physical height could symbolize status and authority. Over time, the idea of being literally higher than others turned into the figurative idea of looking down on them.
Today, people use the phrase critically, not literally. If someone starts speaking in a moralizing or superior way, another person might say that they are on their high horse.
- Example: He got on his high horse about table manners, even though he was late and rude.
- Contrast: Giving helpful advice is not the same as being on your high horse. The phrase implies arrogance, not simply concern.
So the idiom connects an old status symbol, a high horse, with a modern social meaning: acting above everyone else.