Commentary on Meditations: B6:32

I am made of body and soul. Now to the poor body all things are indifferent, as it cannot even make any distinction. To the mind all that is not its own activity is indifferent: and its own activities are all in its control. But within these the mind is only concerned with the present: its activities in the future and in the past are also indifferent at any present moment.

Marcus makes clear delineation about things in his control versus things out of his control.  Things out of his control are indifferents and he (his mind) can have any opinion about them that he wants.  As to time, the only thing relevant to him is the present.  There is nothing that can be done to change the past and we only have control over the future to the extent of our plans.  But a million different things could change those plans in an instant.  Therefore, we really have no control over the future either.

(see also Citadel p. 113, 131-132)