Master Shi Heng Yi "
..Self mastery means you have become very good, very proficient in something relating to yourself. One of these things means you are able to just remain in balance and just remain in peace and just remain calm where other people, normally other people, in your situation would lose their mind , would lose their patience , would lose their temper.
But you have found something about yourself ,you are able to adjust yourself. You know what is influencing yourself
and you know if you want to let other things influence you or not...
So self mastery means learning more about yourself."