Memento mori

Memento mori (Latin for 'remember that you [have to] die'^[1]) is an artistic figure of speech. It is a reminder that nobody can avoid death. It has been written on many gravestones.

References

1. Literally 'remember (that you have) to die' Archived 2016-08-23 at the Wayback Machine, Oxford English Dictionary, Third Edition, June 2001.