Said sarcastically or mockingly to someone who just finished telling a story about some problem or issue in their life that sucks but you don't really care about.
Goorgen: Dude, my girlfriend just dumped me, I got fired from my job, and now my mom won't let me playWorld of Warcraft anymore.
When some resigns or retires from a job, they are on "eternity leave". This can also refer to someone who has passed away, especially someone who worked somewhere for a long time, retired/resigned, then passed away later.
Oh I'm sorry, you didn't know that Kelly is on eternity leave? She resigned and moved to Hawaii!
With regrets I would like to inform you that my boss is officially on eternity leave. I will never see or hear them again. Ever.