A system survives if it gives back more than it costs. Every time your diary saves you a phone call or a scramble, you have bought yourself a little more willingness to open it tomorrow.

What the research says

A systematic review with meta-regression set out to identify which behaviour change techniques explain why some interventions keep working and others do not. Whether something is maintained turns on how it is designed, not on the willpower of the person using it. The review looked at physical activity and eating in overweight and obese adults, so the specific techniques it names come from that setting.

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