If you have been told that anger passes quickly, that is only half true. Roughly half of episodes do settle inside the hour, which also means the other half are still going.

What the research says

In three small experimental studies, people who dwelt on a past provocation felt as though it had happened more recently than it actually had, which is part of why a grudge stays fresh. A separate laboratory study of 69 couples found aggression was highest when dwelling was high, reframing was rare and alcohol was involved. Both are small and run in controlled settings, so read them as a direction rather than a measure of your own hour.

Strength of evidence: one line of research. A single study, or a theoretical account.