Now draw a fourth circle and choose everything about it: how big, where on the page, which way round, where you start. Notice how much heavier that feels.

What the research says

In a meta-analysis of brain imaging studies, people with mood and anxiety disorders who deliberately reinterpreted a situation used the same frontal and amygdala system as everyone else but with altered activation, suggesting the capacity is present and runs less efficiently. If deliberate control feels like heavy work to you, that is a recognisable finding rather than a personal failing. Averages from scanners say little about a given person on a given day.

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