Joy in the Face of Death
The Talmud (Brachot 31) relates that at the wedding of Mar, the son of Ravina, the Sages asked Rav Hamnuna to sing a song. This is what he sang: "Woe to us that we die! Woe to us that we die!"
Since we have an obligation to rejoice with the bride and groom at a wedding, how was it proper for Rav Hamnuna to say something that would cause sadness?
When you are able to recall death and nevertheless rejoice, this is true joy. This is possible when one is committed to serving the eternal God. But if someone needs to forget death in order to rejoice, the joy is incomplete.