This weekend I had a blast slipping and sliding on the ice. My INFP aunt thought I was completely out of control on the ice, but the second I was done I simply stood up and tried something else. When you see someone on ice with arms flayling in the air, feet going 90MPH, then just stop and stand like he was somehow in control the entire time you just found an ISTP.
I lack the fear in the same way an INFP lacks the fear from Fi. I use it when I take my sons hand on the ice and make sure he doesnt fall. I also use it to chip away a little 3 inch square in the ice and fling my son around and let him slip and slide with out fear of falling. I take this in the same direction playing with my son like a doll, flipping him over my shoulders, around my back, lifting him up in the air with one hand and dropping him to catch him. He has complete trust in me. This pretty much extends to everything in the physical world.
I do get in trouble as others tend to follow me and get themselves hurt.