The single worry. περισπᾷ — "pulls aside, distracts" (a military and school word: περισπασμός, a diversion of forces): of everything that can tug at the soul, Marcus leaves one tug legitimate — "that I might myself (αὐτός — emphatic) do something" against the human constitution. All other fears have been dismantled by the preceding passages (7.14, 7.16: from outside there is no harm); there remains the single source of real evil — one's own act. Fear compressed to this point ceases to be fear and becomes conscientious vigilance.

The triple filter: what, how, when. The formula has juridical precision: to do what "DOGMAthe constitution of man does not will" (ὃ οὐ θέλει) — an error in the object; "or in a way it does not will" (ὡς οὐ θέλει) — an error in the manner; "or what it does not will just now" (ὃ νῦν οὐ θέλει) — an error in the time. An act must be right three times over: the right thing, in the right way, at the right moment — otherwise even a good deed, done coarsely or unseasonably, falls out of κατὰ φύσιν. This is a micro-taxonomy of the fitting act: for the Stoa appropriateness is not a binary property but an alignment along every axis at once (cf. 7.11 — the singleness of the measure; 10.2 — "see what your nature demands").

κατασκευή. "The constitution of man" — κατασκευή, the build, the design: the same notion that in 7.7 silently underlies the soldier built for a joint assault, and in 7.13 the framing of rational beings "for one joint work" (κατεσκευασμένα — the same root!). The human being is an artefact with a purpose; the only real failure of the artefact is to work against its own design. The governing discipline is action; the sustaining one, assent (the triple filter is a procedure for auditing the judgment behind an act).