Commentary on Meditations: B12:23

Any one individual activity which comes to an end at the appropriate time suffers no harm from its cessation: nor has the agent suffered any harm simply because this particular action has ceased. In the same way, then, if the total of all his actions which constitutes a man's life comes to an end at the appropriate time, it suffers no harm from the mere fact of cessation: nor is the agent who brings this series of actions to a timely end exposed to any harm. The time and the term are assigned by nature sometimes man's own nature, as in old age, but in any case by the nature of the Whole, which through the constant changing of its constituent parts keeps the whole world ever young and fresh. Now anything which benefits the Whole is always fine and ripe. It follows that for each of us there is certainly no harm in the cessation of life, as there is no shame either — not self-chosen, not damaging to the common interest. Rather there is good, in that it falls in due season for the Whole, thereby both giving and receiving benefit. Thus too a man walks with god's support when his choice and his direction carry him along god's own path.

There is not much to add in the form of commentary here.  Marcus simply expounds, in some detail, the nature of death.  He firmly believes that whenever someone dies, it is at the appropriate time.  Some people might take exception to that sentiment.  For example, consider a young husband and father, who provides for his wife and four children.  He does his best to care for them; he keeps himself in shape; he participates in the community.  In fact, many would agree that there are far too few people like him - the world needs more people like him.  But as fate would have it, he dies at the age of 42.  Is this an appropriate time?  Many would loudly and angrily cry, "no!"  They may even say, "how could a God do this?  His wife, his young sons, his parents, his community - they need him!  Why, God?"

Humans will do all sorts of things to come up with reasons as to why this would happen.  Perhaps there is a reason or multiple reasons for this.  The answers remain hidden to us.

All we can do - all that is left in our power - is to carry on and do what we can to have a positive attitude.  Those of us left still must carry the cause forward.  Those who have passed on, no longer have the power to influence this life.  The task remains to those who still live.

Marcus, after all was written and thought about and contemplated, seemingly had an unwavering trust in the Universe.  "... there is a good, in that it falls in due season for the Whole, thereby both giving and receiving benefit."  A man who can see the good and benefit in the toughest of circumstances, "walks with god's support."  In short, as Nietzsche said, amor fati.