The testing of Sanchin Kata is also very important for the testing of the mind and it's ability to recover. People who are unaccustomed to being hit tend to 'freeze'' when hit and go into a panic mode. This type of pain is unfamiliar as they have never encountered it before and fear settles into their heart. At this point, their odds of escape are about zero.
Sanchin testing helps alleviate this fear. You learn how it feels to be punched...and you learn that you are okay. Your mind does not become unsettled. Overtime, the physical and mental recovery time is shorter and shorter. Your body and mind becomes accustomed to the contact and it ceases to be a struggle.
Being able to recover swiftly after receiving a blow is important, especially if you are surprised or blindsided with an attack. Quick recovery allows you to 'forget' about the body, stay calm and focus on your immediate purpose...defend (disrupt purpose) and escape (restore harmony).
One of my favorite stories about the effectiveness of Sanchin comes from a friend of mine, Mike Iott. Mike and I rose through the ranks together and he eventually became an MP (military police) in the Army. He related to me a time he had to arrest a soldier and upon trying to restrain him, the soldier punched Mike very hard. The soldier shouted proudly, "I got you!". Mike responded back, "Yes, you did, but the question you have to ask yourself is, 'Did you hurt me?'" After this the soldier went quietly.
So, even though Sanchin is usually taught as an exercise in physical conditioning, which it is...it is also very important, if not more important, to your mental conditioning. The ability to mentally recover, in essence to regain your calm (the first battle) is more easily won by means of Testing.
Shihan Dean would also, during kumite, never allow us to stop fighting after we got hit. He would scream at us this is not a tournament and not point fighting. Never stop upon getting hit. Let it go and stay on your purpose. Same advice goes for life as well.
Hands palm to palm,