Your Opinions are What Troubles You
It is not things themselves (πράγματα) that disturb us, but our opinions (δόγματα) about those things.
ταράσσει: the neuter plural subject (τὰ πράγματα) takes a singular verb, as usual (G. 496; S. 958).
τὰ περὶ ... δόγματα: supply ταράσσει from the previous clause. Dogmata is another key term: our opinions and assessments about life, goodness, badness, etc., which condition all our mental states, including all emotions (Smith 2014, 94 n. 6).
ἐπεὶ καὶ Σωκράτει ἂν ἐφαίνετο: unfulfilled possibility, “since it would also (καὶ) have appeared (so) to Socrates.” The protasis is implied: “if death were terrible.” Note that the imperfect indicative can be used to denote an unfulfilled action in the present or, as here, in the past (G. 649; S. 2292.1).
Σωκράτης: on Socrates’ significant influence on the Stoics and Epictetus, see the Introduction, Predecessors.
ἐμποδιζώμεθα ... ταρασσώμεθα ... λυπώμεθα: 1 pl. pres. pass. subj. in a temporal clause, equivalent to a conditional + imperative construction
αἰτιώμεθα: > αἰτιάομαι, 1 pl. pres. mid. subj.; hortatory subj. (G. 472; S. 1797) with μή as the negative (here μηδέποτε): “let us never blame,” “we must never blame.”
ἑαυτούς, ἑαυτῶν: Epictetus at times uses the third plural reflexive form of the pronoun where we would expect first person pronouns (S. 1230). Translate “ourselves” and “our” for the sake of consistency in English.
τουτέστι: “that is,” “that is to say”
ἔργον τὸ ἄλλοις ἐγκαλεῖν: supply ἐστί. τὸ ... ἐγκαλεῖν: articular infinitive (G. 574–575; S. 2025): “blaming others is the act.”
ἐφ' οἷς: “at times which,” i.e “when.” The antecedent has been omitted (G. 614; S. 2509).
ἠργμένου: > ἄρχω, perf. mid. part., gen. masc. sg. “of one beginning” (philophical studies).
πεπαιδευμένου: perf. mid./pass part.; “of the one who has been educated” = “of the one who has assimilated the philosophical principles.”
τὸ ἑαυτῷ ... τὸ μήτε ἄλλῳ μήτε ἑαυτῷ: supply ἐγκαλεῖν from the previous sentence, and ἔργον ἐστί as the predicate in both clauses: “blaming oneself is the act of (one) beginning to be educated, etc.”