Do every deed, speak every word, think every thought in the knowledge that you may end your days any moment. To depart from men, if there be really Gods, is nothing terrible. The Gods could bring no evil thing upon you. And if there be no Gods, or if they have no regard to human affairs, why should I desire to live in a world void of Gods and without Providence? But Gods there are, and assuredly they regard human affairs; and they have put it wholly in man’s power that he should not fall into what is truly evil. And of other things, had any been bad, they would have made provision also that man should have the power to avoid them altogether. For how can that make a man’s life worse which does not corrupt the man himself? Presiding Nature could not in ignorance, or in knowledge impotent, have omitted to prevent or rectify these things. She could not fail us so completely that, either from want of power or want of skill, good and evil should happen promiscuously to good men and to bad alike. Now death and life, glory and reproach, pain and pleasure, riches and poverty—all these happen equally to the good and to the bad. But, as they are neither honorable nor shameful, they are therefore neither good nor evil.
Marcus was obsessed with death, and rightly so, since death alone gives the rest of this any meaning. If the gods exists, then surely you want to meet them having lived an honorable life. If not, surely you do not want to be on your death bed wishing you’d done things differently. The outcome is the same, do what was in you control, live a moral life, and die in peace.