A question and an answer in six words. The passage is built as a ready two-beat formula: the question — TERMΠεποίηκά τι TERMκοινωνικῶς; ("have I done something socially?") — and the immediate conclusion DOGMAοὐκοῦν DOGMAὠφέλημαι ("then I have been benefited"). There are no premises between them: the connective οὐκοῦν ("therefore") sets the conclusion down as self-evident.
The form of the verb decides everything. ὠφέλημαι is a passive perfect: "benefit has already accrued to me." Not "I shall benefit others," not "I shall be repaid," but: by the very doing of the social act I have already come out ahead. The reward does not follow the deed in time, it coincides with it. This also disposes of the question of gratitude: there is nothing to receive, because it has been received. Cf. 5.6 — the three kinds of benefactor, the third of whom is like a vine that has borne its cluster and seeks nothing further; and 9.42 — the eye demands no payment for seeing.
Why this stands beside 11.1. The book's first passage says that the rational soul "harvests itself the fruit it bears," whereas the fruits of plants go to others. Here the same thought is compressed into a working formula — and that is the difference of genre: 11.1 argues, 11.4 hands over.
Instructions for use. EXERCISEτοῦτο ἵνα ἀεὶ EXERCISEπρόχειρονEXERCISE ἀπαντᾷ — "let this always meet you ready to hand." Πρόχειρον is the school's term for a short formula kept in readiness (Epictetus, Ench. 27, 52). The verb ἀπαντάω ("to come to meet") makes the formula active: it is not you who recall it, but it that comes out to meet the occasion. And the close: μηδαμοῦ παύου — literally "nowhere leave off"; an adverb of place, not of time — that is, in no position, under no circumstances. The governing discipline is action, the sustaining one assent.
A note on punctuation. The first clause is printed as a question (Πεποίηκά τι κοινωνικῶς;) — so el.wikisource, and so both translations read it; the stub carried a raised stop (·) in its place, which turned the question into a statement and destroyed the two-beat structure.