On a skull in the ossuary of the Romanian Skete Prodromos on Mount Athos one can read the following inscription in Romanian: "Ce sunt eu, vei fi și tu. Ce ești tu, am fost și eu." (translation: What I am, you will be, too. What you are, I've been myself.), reminding the reader of the ephemerality of his life and the constant need to think of his own death.
Credit: adriatikus en:commons:talk / Photograph created using a Canon PowerShot A530 camera and modified in GIMP 2.2.14.