In chapter 1 of Book 10, Marcus opens up and, as if with a sigh, wonders if he'll ever make moral progress. He makes a really good outline, in the form of a question, as to what he thinks the ideal is.
What makes that ideal soul?
Being good and simple; having integrity and being positive. It is a disposition of love and affection for others.
The ideal soul does not desire anything - no needs, no passionate desires, no pleasures, no coveting of a better place or space or climate, no wish for good company - other than simply desiring things as they are. The ideal soul loves what is, without extending the reach of desire for anything else.
The ideal soul loves its fate (amor fati) and all that life sends to it. The ideal soul embraces what the Gods sends to it. The ideal soul loves the Gods or the Universe or Fate.
The ideal soul gladly accepts change in all forms.
The ideal soul never criticizes the gods or men.
To me, this passage is exceptionally close to the notion Friedrich Nietzsche tried to capture when he said, "My formula for greatness in a human being is amor fati: that one wants nothing to be different, not forward, not backward, not in all eternity. Not merely bear what is necessary, still less conceal it...but love it”