We should anchor our thought in that which is most certain: the fact of change, the nearness of death, that things exist, that one is conscious, that one can say 'I' and mean it, the fact of conscience. But man does not meditate on the certain; he chases after the uncertain and ephemeral: name and fame, power and position, longevity and progeny, loot and land, pleasure and comfort.
Wealth is not certain, but the grave is. So meditate on death, asking: Who dies? Who survives? What is death? Who am I? What am I?
Death is certain, but the when is uncertain. Do not try to make a certainty out of what is uncertain, or an uncertainty out of what is certain.
"What is your life? You are a mist that appears for a little while and then vanishes." (James 4:14)