我事に於て後悔せず is a vow, not a command. One man says it of himself: he does not look back on what he has done. It is one of twenty-one lines, each in the first person, and all but one name a thing he does not do. A person who chooses it takes Musashi's own sentence about himself. Whether to read it as his rule or to take it as your own is yours.
The English title turns the vow into advice to the reader. The Japanese keeps the first person: I regret nothing I do.
The English title is from Kenji Tokitsu's Miyamoto Musashi: His Life and Writings of 2004, in Sherab Chödzin Kohn's translation.
Musashi brushed the twenty-one articles on one sheet, dated by its colophon and by the school's chronicles to the twelfth day of the fifth month of 1645, a week before his death; the prefecture that holds the sheet judges that colophon, with its address to his pupil Terao Magonojō, a later hand, while the one scholar to study the sheet as a text, in 1967, reads it as Musashi's own, written on another day.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 我事に於て後悔せず.