Behaviour

Where returns are actually lost.

The pattern

Investors reliably buy after rises and sell after falls, capturing less than the funds they hold. The gap between fund returns and investor returns is measured and consistent.

Loss aversion makes falls feel far worse than equivalent gains feel good.
Doing nothing is an active and usually correct decision.

Automation

Regular fixed contributions remove the timing decision entirely. Rebalancing on a schedule rather than a hunch does the same for allocation.