let's start at the beginning. both my beginnings with rationality and the first place you should start to find the winning way.
by now the metaphor seems well worn to me, but i have to remember that there was a time when i didn't know about it. a time when i could get confused about the correspondence between my own thoughts and reality. and even a time when i had the words to separate the two but could still get things confused. so let me try to ease you in to our first attempt to break and reintegrate your thinking: the metaphor of the map and the territory.
a wise king commands a map of perfect detail be made of his kingdom. the map makers begin the project. animals in their own and neighboring kingdoms are slaughtered to make the parchment. forests are cleared to collect all their resin and giant holes are left in the ground from extracting graphite to make the ink. the army of map makers works furiously day and night until at last they tell the king the project is finished. in the morning, they say, the map shall be revealed to him.
when the king wakes up he notices it's unusually dark. looking out the royal window, he sees that the sky has turned a yellowish tan and the light is blocked out. he stares at the sky, examining the lines that seem to have replaced the sun and clouds. slowly realization dawns on him: the sky has been replaced by a map!
the king runs downstairs, still in his nightgown, calling for his map makers. the king throws open the doors of the throne room to find them gathered, nodding and smiling to themselves.
"what is the meaning of this?!?" he bellows.
"why, sire," the head map maker says, "we have completed the project as requested. you need now only look up to see a perfectly accurate map of the kingdom in the sky."
it's easy, in hindsight, to see the king's confusion. in asking for a perfectly accurate map, he got the only thing that could be perfectly accurate: an exact reflection of the kingdom. in fact, in this story, i'm disappointed the map makers didn't manage to achieve greater accuracy by not constructing a map at all and just declaring the kingdom to be the map of itself. to literally make the map the territory.
when we talk of maps what we really want are smaller versions of reality that we can carry in our pockets. or, less metaphorically speaking, thoughts we can use to model the world.
this is one of the things folks mean when they say that the map is not the territory: the map serves a different purpose than the territory, and it would be impractical to use the territory as a map. or, to again the break down the metaphor, models are useful because they are thoughts we use to reason about the state of the world. there can be no such thing as a perfect model: all models contain error and uncertainty. you cannot be 100% or 0% sure of something. probability is subjective; beliefs contain uncertainty.