Genre and place in the book. A quoted aphorism — the only direct saying of PERSONEpictetus in Book 4, an inset in another's voice. A sharp formula of Stoic dualism: you are the soul, while the body is merely a corpse you carry about.
Ψυχάριον — "the little soul." A diminutive of TERMψυχή with a self-deprecating shade: not the grand "soul" but the "poor little soul." Yet even this little soul is you (εἶ, "you are"); the body is no part of the "I." It chimes with Med. 10.38: the real "man" is the hidden inner thing that pulls the strings, not the "vessel" and the organs attached to it (DOGMAthe self is in the ruling faculty, not in the flesh).
Νεκρόν — "a corpse." The body is called a corpse — a bare EXERCISEdefinition that strips it of all value: what you carry about is already dead matter (cf. Marcus's definitions of the body — 02-02 "blood-slime, little bones, a weaving of nerves"; Med. 8.24; 9.36). The image both devalues the body (there is nothing in it to prize) and recalls mortality.
Source. The saying is PERSONEpictetus's, preserved only here, in Marcus; it is kin to the Epictetan move "the body is clay, not ours" (Disc. 1.1).
The disciplines. The principal one is assent: the right view of oneself (you are a soul, the body a corpse) is a bare EXERCISEdefinition of the human being. The secondary is desire: hence detachment from the body and from bodily things, in which there is nothing to prize.
Parallels. I am the inner ruling thing, not the vessel — Med. 10.38 (cf. DOGMAself-is-hegemonikon). The body in its bare nature — dead matter — 02-02; Med. 8.24; 9.36 (cf. EXERCISEdefinitio). The soul/body dualism in Epictetus — Disc. 1.1.