While the functions normally maintain a very unique position in a person's repertoire, when and how you use them will vary, especially at the day-to-day level. In short, PEOPLE CHANGE. Monitoring a constant in the sea of chaos is a most daunting and nigh impossible task. Anyone with 100% certainty of their type must be ignoring these truths in some way.
That's actually a very eloquent way of putting it. I agree.