The only way to fend off the nagual is to remain unaltered. The nagual is only for witnessing. So, we can talk about what we witness and about how we witness it. You want to take on the explanation of how it is all possible, though, and that is an abomination. You want to explain the nagual with the tonal. That is stupid. We make sense in talking only because we stay within certain boundaries, and those boundaries are not applicable to the nagual.
To be a perfect tonal means to be aware of everything that takes place on the island of the tonal. It takes a gigantic struggle to clean the island of the tonal.
We interpret any unknown expression of the nagual as something we know. The nagual might be interpreted as a breeze shaking the leaves, or even as some strange light, perhaps a lightning bug of unusual size. If a man who doesn't see is pressed, he would say that he thought he saw something but could not remember what. This is only natural. The man would be talking sense. After all, his eyes would have judged nothing extraordinary; being the eyes of the tonal they have to be limited to the tonal's world, and in that world there is nothing staggeringly new, nothing which the eyes cannot apprehend and the tonal cannot explain.
In order to be an average tonal a man must have unity. His whole being must belong to the island of the tonal. Without that unity the man would go berserk; a sorcerer, however, has to break that unity, but without endangering his being. A sorcerer's goal is to last; that is, he doesn't take unnecessary risks, therefore he spends years sweeping his island until a moment when he could, in a manner of speaking, sneak off it.
The whispering of the nagual will come at times and then vanish. Don't be afraid of it, or of any unusual sensation that you may have from now on. But above all, don't indulge and become obsessed with those sensations.
A warrior is, let's say, a prisoner of power; a prisoner who has one free choice: the choice to act either like an impeccable warrior, or to act like an ass. In the final analysis, perhaps the warrior is not a prisoner but a slave of power, because that choice is no longer a choice for him. He cannot act in any other way but impeccably. To act like an ass would drain him and cause his demise.
An immortal being has all the time in the world for doubts and bewilderment and fears. A warrior, on the other hand, cannot cling to the meanings made under the tonal's order, because he knows for a fact that the totality of himself has but a little time on this earth.
A warrior cannot be helpless, or bewildered or frightened, not under any circumstances. For a warrior there is time only for his impeccability; everything else drains his power, impeccability replenishes it.
Impeccability is to do your best in whatever you're engaged in. The key to all these matters of impeccability is the sense of having or not having time. As a rule of thumb, when you feel and act like an immortal being that has all the time in the world you are not impeccable; at those times you should turn, look around, and then you will realize that your feeling of having time is an idiocy. There are no survivors on this earth!
Turn off your internal dialogue and let something in you flow out and expand. That something is your perception, but don't try to figure out what I mean. Just let the whispering of the nagual guide you.