I bet we'd get a lot of different definitions if we asked multiple people to define "emotional mastery". To me all it really means is understanding how emotions come and go and being competent with tools for dealing with emotions so that they are no longer running your life. It requires diligence, courage, and life-long commitment. Someone with a fair level of emotional mastery is going to understand impermanence on a deep level. That is to say that emotions don't last, but neither does transcendence or the quality of our practice.   Here is what I've learned about the nature of emotion:   It is true that some emotions stop arising in certain situations, particular through repeated exposure. Emotions also stop arising as we heal from trauma and loss. Sometimes emotions don't go away, but the intensity lessens. Other times emotions return or increase in intensity as our exposure to them lessens or when we stop practicing. The last thing I've realized is that life is always changing so we will always have emotional reactions as life throws new challenges at us.   I don't like the term emotional mastery because it implies a destination or transcendence or some other bullshit like that. However, I do believe that we can tap into equanimous states with increasing frequency as our understanding and commitment deepens.