why cant i quit when i know my health and well being is in danger?

[Lukas W]

me and my friend do jui-jitsu and we all ways practice on each other.The thing is when he gets me into a submission and it really hurts i don't tap out.like the other day he had me in an arm triangle chock for 30 minutes and i didn't tap or lose consciousness.And surprisingly i got out.i don't know why my body is able to do this.maybe its just a strong will.does anyone know what this is. P.S. yes he had the chock in tight and when i got out my face was red and the pressure was killing me