“I don’t envision a single thing that is as quick to reverse itself as the mind—so much so that there is no satisfactory simile for how quick to reverse itself it is.”
AN1.49: Lahu-parivaṭṭa Sutta
Lahu-parivaṭṭa Sutta: Quick to Reverse Itself - translated by Thanissaro Bhikkhu
Translated by Thanissaro Bhikkhu. Source text via dhammatalks.org.