Consistency - steadfast adherence to the same principles, course, form.
You need it in your training. Be it in the martial arts or any other sport.
You need it when you go to school. You need it when you work.
You need it when raising a child. (extremely important)
I appreciate consistency. Especially when you set standards and expectations.
If you set particular standards you must be consistent in the way you judge others by those standards.
If you change the standards and criteria or become lax in your consistency in up holding those standard it can give the sense of weakness. (It also makes me crazy.)
I bet ninjas are very consistent in their training, their thought process, beliefs and standards they live by.