Plutarch on how to work on one’s anger:

“My pledge was to begin by spending a few days doing the equivalent of going without drinking and alcohol – avoiding anger. … And then to spend a month, two months, doing this … In this way, by experimenting on myself, the period of time gradually got longer and I progressed towards increased tolerance, by using self-control to pay attention to myself and to keep myself composed and imperturbable – maintaining a holy silence – and to remain untainted by pernicious speech, unnatural actions and emotion.”