The Twenty-One Precepts of Miyamoto Musashi: the Dokkodo. Complex and difficult to understand, nonetheless valuable.

woodblock print courtesy of wikipedia: Miyamoto Musashi using his two-sword technique
If you thought the nine rules were hard, here are Miyamoto Musashi’s 21 precepts– infinitely harder (from Wikipedia):
(I have added in quotes the interpretation of the Dokkodo from Hyoho)
- Accept everything just the way it is.
“In no way should one act contrary to the great future that you have before you.”
- Do not seek pleasure for its own sake.
“Do not try to look for an easy life because in this world there is no such thing.”
- Do not, under any circumstances, depend on a partial feeling.
“Never harbor prejudice or an attitude about everything.”
- Think lightly of yourself and deeply of the world.
“Consider your own superficiality and try to have profound thoughts of others.”
- Be detached from desire your whole life long.
“To always be detached from desires or wants.”
- Do not regret what you have done.
“Never have regrets about oneself or what you have done.”
- Never be jealous.
“There should be no mind of envy or wrongdoing.”
- Never let yourself be saddened by a separation.
“Never have a mind of envy or attachment to all things.”
- Resentment and complaint are appropriate neither for oneself or others.
“There should be no thought of bearing a grudge against each other.”
- Do not let yourself be guided by the feeling of lust or love.
“There is no mind of thinking about a love life.”
- In all things have no preferences.
“One should not have likes or dislike for things.”
- Be indifferent to where you live.
“Do not have preference for a particular domicile.”
- Do not pursue the taste of good food.
“As to the choice delicious food with a relation to society in general.”
- Do not hold on to possessions you no longer need.
“One should never let future generations become attached to old weapons.”
- Do not act following customary beliefs.
“One should avoid superstition and taboo.”
- Do not collect weapons or practice with weapons beyond what is useful.
“To use equipment that you consider important and not keep that which is of no use.”
- Do not fear death.
“Follow your way with preparedness for death.”
- Do not seek to possess either goods or fiefs for your old age.
“As you get old your gained possessions are of no use.”
- Respect Buddha and the gods without counting on their help.
“Respect the gods and Buddha but do not count on them.”
- You may abandon your own body but you must preserve your honour.
“Do not abandon your good name even if it means sacrificing your life.”
- Never stray from the Way.
“Do not stray from the path of Hyoho.”
A deeper discussion of the “Dokkodo” by a master of “Hyoho” leads to confusion in English. Clearly there are subtleties of meaning, but the translation given in Wikipedia (numbered above) is simpler and more sensible.