Think often about how quickly everything passes away and disappears. All things flow like a river. All actions are always changing. Even the causes behind events shift constantly. Almost nothing stays the same. Then consider the endless time that came before us and the vast time that will come after. Everything will dissolve into nothing.
Again, often meditate how swiftly all things that subsist, and all things that are done in the world, are carried away, and as it were conveyed out of sight: for both the substance themselves, we see as a flood, are in a continual flux; and all actions in a perpetual change; and the causes themselves, subject to a thousand alterations, neither is there anything almost, that may ever be said to be now settled and constant. Next unto this, and which follows upon it, consider both the infiniteness of the time already past, and the immense vastness of that which is to come, wherein all things are to be resolved and annihilated.