Why does schemas about people fail?

The most common reason schemas about people fails: Believing you see people clearly while everyone else operates on assumptions. The most dangerous person-schemas are the ones that feel like perception rather than interpretation. When you say 'I'm just being realistic about human nature,' you're describing a schema — not reporting a fact. The people with the most rigid person-schemas are usually the ones most convinced they don't have any.

The fix: Pick three people you interact with regularly — a colleague, a family member, a friend. For each, write down your default assumption about their motivation. Not what they do, but why you assume they do it. ('She argues because she needs to be right.' 'He's quiet because he doesn't care.' 'They volunteer because they want recognition.') Now ask: what evidence would change this assumption? If you can't think of any, the schema is functioning as an unfalsifiable belief — and it's running your relationship.

The underlying principle is straightforward: Your default assumptions about human nature shape every interaction.