When weak or injured always continue training as you should always be able to adapt in any condition.
You must be on your toes constantly, yet be relaxed.
Budo is simply the study of the best ways to kill.
Nature is your friend; it helps you to win. Your enemy will have unnatural movement, therefore you will be able to know what he is going to do before he does it.
Always be able to kill your students
Any place we can breathe, we can do Ninjutsu.