loss aversion

Losing ten dollars feels worse than winning ten feels.

Kahneman and Tversky's 1992 paper established that the pain of losing is approximately 2.25 times more powerful than the joy of gaining.

The 1979 paper introduced the qualitative concept of loss aversion, while the quantitative estimate was determined in the 1992 study.

You are designed to protect what you have, not increase it.

Where this comes from

Study: Kahneman and Tversky, 1979
What the check found: The 1979 paper established the phenomenon, but the quantification of the effect size (the '2x' or 2.25 ratio) was empirically determined in their 1992 paper, 'Advances in Prospect Theory'.
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.