Prashas Emor starts with the special laws that apply to kohanim. Because kohanim are expected to be on a higher spiritual level then everyone else, the Torah requires more of them. One such requirement is that they stay away from corpses. The Rishonim try to give us some sense, in a way that we can relate to, of what "defilement" occurs by being in proximity to a dead body.
Be that as it may, an exception is made for the kohen when the deceased is one of the seven close relatives recognized by halacha. The Sefer Hachinuch (mitzvah 263) explains that the ways of Torah are pleasant (i.e. compatible with human nature) and the Torah did not want to distress the kohanim, for it is a great relief to pour out one's emotion and "gain solace through tears."
And yet, the Torah prohibits a Kohen Gadol from becoming tameh even for one of his seven close relatives. The Sefer Hachinuch (mitzvah 270) explains this difference by saying, "because the [Kohen Gadol]'s soul is bound up with Hashem, totally separated from human nature, and has all but forgotten this physical world, he therefore does not truly mourn his close ones, for even while they are alive, he is already distant from them."
This same distinction between "man" and "superman" is actually the crux of the parsha of Aharon and Miriam's lashon hara about Moshe (Bamidbar 12:1-2). They questioned the appropriateness of his having separated from his wife because of his being a prophet. They pointed out that they, too, were prophets and yet were expected to continue to live normal family lives. Hashem responded to them that Moshe was different. The Rambam (Hilchos Yesodei haTorah 7:7) articulates this difference as Moshe, "having bound himself to the Tzur haolamim [i.e. hashem], never leaving that dveikus."
This concept expresses itself in many aspects of Torah, from the Ramban's stating (Vayikra 26:11) that, "doctors have no place in the house of G-d" to Rav Chanina ben Dosa's reliance on miracles (Berachos 33, 34, and many more.) It is not that there are two Torahs, chas v'shalom; rather there is the Torah for people whose reality is a physical world with the awareness that Hashem is behind it all, and a different set of norms for those who perceive that Hashem is the reality.
The Chazon Ish hints at this at the end of chapter two of Emunah V'Bitachon. Throughout the chapter the Chazon Ish stresses that genuine bitachon requires engaging with the world and believing that Hashem is doing what is best regardless of whether things turn out the way we would like them to. And yet, he hints at the end of that chapter, that a person who is on an extraordinary level of bitachon can actually sense the concurrent hasgacha and be aware that everything will be well.
I think that this principle is an important one to explain to our children when telling stories of great people that describe deeds that are commensurate only with a very high madreiga. For instance, there is a well-known story of the Vilna Gaon only greeting his sister for a very short time after not seeing her for many years and then immediately returning to his learning. When sharing that story, one must emphasize that for us this would be ignoble behavior, and only on the extraordinarily high madreiga of the Vilna Gaon who, like the Kohen gadol, lived on an entirely different plane and was barely connected to this world, is such behavior appropriate. It is not that there are different rules for different people, per se. Rather, there are different rules for different circumstances. Loss of kin is a genuine tragedy for humans living in the world that the vast majority of us live in. But for those humans leaving in a higher world than ours, death is merely the transition to the next phase of life.