If a mistake is repeated time and again, one must take atonement.  Specially if the mistake is such that it harms the mission, or the organization, or others , one should not wait for a similar mistake to be repeated again. Instead, one should take atonement immediately. Atonement reduces the severity of  Karmaphal (fruits or consequences of the action) of that act. Hence, penance must be such that pinches the mind, for instance,  doing something that induces physical pain for us, but benefits the society. – Tanuja Thakur