Mastery it is an inside job
Much of life tells you to master, pay attention to, and that external matters will make you happy.
A house, success, sex, reputation, cars, wealth ad on and on will make you happy. Winning will make you happy. Love will make you happy. Religion will make you happy. Relationships will make you happy. Self improvement will make you happy.
Well that last one just might. But the others? Not for long. Besides the fact we can not take any external happiness with us. External changes do not change the internal state of our being for long. Yes you are happy after achieving any of these external things. But in the long term they do not permanently change the one’s internal state. So people revert to living out their internal being — ness.
Thus our internal bing-ness is more important. Thus mastery is self mastery, an internal job. Mastering a job is fun and can provide some career/lifestyle security which is an important part of life. We need external security. We need a monetary income source. Yet none of these externals provide lasting contentment. Take the externals away and see what you have left.