Know, that when Adam haRishon sinned, he damaged all of the sparks ("nitzutzot") of his Nefesh, his Ruach, and his Neshama. The concept is what we already know, that just as the body of an Adam (a person) includes many sparks, (and these sparks comprise) the 248 limbs and 365 sinues of a body, [so too, each limb is subdivided into many parts], there are many sparks in his head, so too in his eyes, and so too in each and every limb.
So too, his Nefesh [also comprised these], just as it was explained in Midrash Tanchuma and in the Midrash Rabbah in Parshat Tisa on the passuk "איפה היית ביסדי ארץ" (edit this, please, and add in missing parts.) And when Adam haRishon sinned, he damaged most of the sparks of his Nefesh, of his Ruach, and his Neshama, and they fell into the Klipot. This is the secret of what is written in the Sefer haTikkunim in the Hakdama on the passuk "כצפור נודדת מקנה" (a bird flying from one birdhouse to another).
Because, just like the Shechina goes into the Klipot [to save a person], so too the Tzaddikim also release him (they "fish him out" from the klippot) -- they go into galut from place to place, and if there is a spark (of kedusha), the release it from its place [where it was trapped in the klipot]. "Head in head," [meaning, the sparks that were in the 'head' of kedusha fall to the 'head' of klipah], "eye in the eye," [same concept], etc. And this is the secret of the concept that both Kain and Hevel (his sons) sinned in different sins [notwithstanding the sin their father Adam did], so their sparks (nitzutzot) sunk into the depths of the klipah: