Commentary on Meditations: B5:34-35

You can always ensure the right current to your life if you can first follow the right path - if, that is, your judgements and actions follow the path of reason. There are two things common to the souls of all rational creatures, god or man: they are immune to any external impediment, and the good they seek resides in a just disposition and just action, with this the limit of their desire.

If this is no wrongdoing of mine, nor the result of any wrong done to me, and if the community is not harmed, then why do I let it trouble me? And what is the harm that can be done to the community?

These two passages are largely centered around the discipline of assent (controlling our judgments and perceptions).  There are also references to the discipline of action ("just action") and the discipline of desire ("with this the limit of their desire").

Nothing outside our "inner citadel" can harm our soul.  We, as individuals, are the only ones who can control our perceptions.  Hence Marcus says, "all rational creatures, god [and men] ... are immune to any external impediment."  We get to decide our attitude.  We get to decide how to react to events and things out of our control.

Furthermore, we as individuals, can choose to have a "just disposition" (good attitude) and when and how we serve others ("just action").

We limit our desires to what is - to what happens.  We should love what happens - amor fati.

In summary: have a good attitude; serve others; love your fate.

In second passage (35), Marcus discusses a specific aspect of the discipline of assent.  Why let anything bother you if no harm has been done to the community and you have done no harm?

(see also Citadel p. 241)