You will never master the Self, yet it should be your life's work to try.
Perhaps mastery just happens in specific moments; perhaps the journey, is, in fact, more important than the destination. The physical world is too malleable and uncertain to contain Heaven or Nirvana. What is left is the Way--the Tao--the path back to one's Self.
And the Self is a sword blade that can cut all things around it, but never cut itself. We must try to keep that blade as sharp as possible. Our Minds need training and discipline.
"Nirvana is reached by that man who wisely, heroically, trains himself," suggests the Dhammapada texts.
Mastery, to the followers of Buddha, is to be found in the transcendence of the world's sorrows. Buddha sat under a tree until he mastered Himself; and His enlightenment was lasting. (So on paper, my argument is incorrect).
But most of us are not ascended beings.... at least yet.
So we train. And train some more. We seek after glimpses of Nirvana rather than total enlightenment. For this is our nature... we are seekers. If we found the entire truth, the game would be up. Right?
And maybe then, eventually:
"With the dust of impurities blown off, and free from sinful passions, (we) will come unto the glorious land of the great." (Dhammapada)