The problem is I didn't start behaving like a 6 until recently. I used to act more like a 5, I think. I'm not sure what that means...
Here's my advice:
Stop thinking about it, go out and there and live your life for a while, then come back with a fresh perspective.
I did it by evaluating myself. I do think the easiest way to do it is to observe your fears. What makes you feel fear? Monitor your emotions. Figure out what your basic fear is.
ISTP 6w5 sx/sp