The 5 Commandments of the Ninja

Whenever one is sad, unhappy, sick, wounded, or in despair, one should remember these five commandments.

1. Forget your sadness, anger, envy, and hatred. Let them pass like smoke in one breath. Don’t give in to such feelings.
2. Do not deviate from the path of righteousness. You should live a life worthy of a human being. It is this simple philosophy that has been repeated by sages for many ages. […]
3. Don’t hold on to greed, luxury, or your ego. If you learn the martial arts just for your own benefit and always try to be dependent on others just because it’s easier, you will be controlled by these three desires – even if you have reached a high rank in the martial arts. These three desires distort not only martial arts but also humanity. When people die, there are two paths to death: joy and sorrow. Joy is meant here in the heavenly sense, and not pleasure or the past. When one reaches this stage in life, one realizes one’s true purpose in life.
4. You should accept suffering, sorrow, or hate as it is and see it as a chance from the Almighty for a test. It is the noblest spirit in Ninpō to regard everything as a blessing of nature. When you’re trying to get things done, sometimes your goodwill is portrayed as bad by some people who are obsessed with their own selfishness. […]
5. Be fully engaged in budō with both your time and mind and be deeply focused on Bujutsu with your mind. Read between the lines of the late Takamatsu’s story […] and you will learn the attitudes and methods to be followed in Ninjutsu training. […]

Hatsumi Masaaki, Essence of Ninjutsu