The rules of trading can be summarized in these few sentences:

A sharp drop will have a rebound, don't sell; a slow drop will continue to fall, sell.

A sharp rise will inevitably retreat, sell; a slow rise will continue to rise, don't sell.

A large drop in the morning shouldn't lead to panic selling, there will generally be a rebound in the afternoon.

A large rise at the close should lead to reducing positions, as the probability of a pullback the next day is high.

Sometimes it's very accurate, sometimes it’s not useful at all,

it's just human nature, it's all about cutting losses.