Kuju-Kiri

One aspect of ninjutsu is kuji-kiri, or signs made with the fingers to assist them in self-control during moments of danger.. In practicing kuji-kiri, there were 81 different ways the ninja could knit his fingers together. At the same time, he chanted Buddhist sutras, or maxims from the scriptures.
The practice not only restored confidence and gave the ninja inner strength in moments of danger but also promote a healthy mental state. A ninjas perk was the unbreakable concentration. By using Kuji-Kiri a ninja would focus and calm their mind. Within seconds a ninja became so focused they could read their opponents spirit, mind, and body. This is a very special skill for a ninja to posses for dealing with life and death situations.