More particularly speaking, it is only the upper three sefirot of Atik which are considered to be part of the Self. This may be understood as follows. Each of these two parts of Keter, contain ten sefirot as well. The seven lower emotional sefirot of the pleasure (Atik Yomin) are enclothed in the sefirot of the desire (Arich Anpin) and enliven them. The sefirah of Chesed of Atik (Kindness of Pleasure) is enclothed in Keter of Arich (Desire of Desire). This may be comprehended by understanding what Chesed of Atik is. Being that the general matter here is pleasure, therefore all its particular sefirot, are aspects of pleasure. Chesed is when something spreads forth in great abundance. Therefore, Chesed of Atik (Kindness of Pleasure) represents an abundance of pleasure in something. Now, when there is an abundance of pleasure in something, this enlivens the desire for it. We therefore understand how Chesed of Atik (Kindness of Pleasure) is enclothed in Keter of Arich (Desire of Desire).
Now, as mentioned before, Gevurah (Sternness) is the opposite of Chesed (Kindness). Therefore, if Chesed of Atik represents abundant pleasure in something, Gevurah of Atik represents the pain in something. We now can understand why Gevurah of Atik (Sternness of Pleasure) is enclothed within Chochmah of Arich (Insight of Desire). The Chochmah (Insight) of a desire means that it should be in a specific way, with precision. If nothing was painful, there would be no need for any specific desires, that it should be one way and not the other. It would make no difference at all what we did, because the pleasure for everything would be equal. It is specifically Chochmah (Insight) which determines what is or isn’t desirable. For this reason Chochmah of Arich (Insight of Desire) is the source of the mitzvot (commandments) of the Torah.
(The above principle applies to the enclothement of all the seven lower sefirot of Atik (Pleasure) within the seven upper sefirot of Arich (Desire). An additional example is how Malchut of Atik (Kingdom of Pleasure) is enclothed in Netzach of Arich (Conquest of Desire). Malchut of Atik represents the great pleasure of being the king and ruling over others. It therefore is easy to see why Malchut of Atik is enclothed within Netzach of Arich which represents the desire for conquest.)