Commentary on Meditations: B7:53-54

Where a task can be accomplished in accordance with the reason which gods and men share, there is nothing to be afraid of: because where there is the possibility of benefit from an action which moves along the proper path, following our own human constitution, there should be no lurking fear of any harm.

Everywhere and all the time it is up to you to honour god in contentment with your present circumstance, to treat the men who are your present company with justice, and to lavish thought on every present impression in your mind, so that nothing slips in past your understanding

Simply put, if we use our reason to act and to complete a task, then there is no reason to fear harm.

In the second part, Marcus outlines our duties with regard to God, to others and to ourselves.  Our duty to God is to love our fate - to be grateful for the life God has given us and for what God has sent our way (in other words, apply the discipline of desire).  Our duty to others is to be just toward them (in other words, apply the discipline of action).  And to ourselves, our duty is to think on every impression and understand them (in other words, apply the discipline of assent).

(see also Citadel p. 35, 44, 218)