Self-discipline occurs when there is a mental habit pattern encouraging some further action and the attentional response is to not engage in that habit pattern. This then raises an interesting question, why does it *feel* as if there’s a resource being used up, if the reality is just competing habit patterns in the mind and “voluntary” control over attention, why does it feel like we can run out of willpower. These intensities cannot reach infinity, so there’s always the possibility of someone resisting even the most intense urges when the voluntary control over attention is even stronger, but these are rare because it is very unusual to develop that kind of self-discipline (and probably harmful, in most cases—such as diseases like anorexia or pain-seeking behavior).