on one's high horse

Prepositional phrase

idiomatic

(idiomatic) Self-righteous; proceeding on the belief one is more correct or proper than others.

Japanese Meaning

自分が正しいと思い込み、他人を見下す高慢な態度をとること / 偉そうに振る舞い、自己正当感に満ちている様子

It's easy to get on one's high horse when you think you're always right.

いつも自分が正しいと思うと、偉そうに振る舞いがちだ。

Sense（1）

(idiomatic) Self-righteous; proceeding on the belief one is more correct or proper than others.

When she gets on her high horse there is not much to do but go along with it or wait for it to pass.