What does "feeling like your life is over" mean and why is it not in any dictionary online?

Read also:

• Gold overtakes euro as global reserve asset, ECB says - Financial Times
• What are LGBT+ people tired of hearing?
• Why do Democrats call any Republican "Magats", like they are subhuman?
• How effective will the Senate-passed bill, S. 4569, the Take It Down Act, which would criminalize the publication of non-consensual intimate imagery (NCII) be?
• See how the national debt grew to more than $36 trillion - The Washington Post
• 9 Things Women’s Health Doctors Would Never Do - HuffPost
• Joaquin Buckley shuts down narrative that Islam Makhachev is a 'big threat' to the top UFC welterweights - Bloody Elbow
• What's the most sordid activity you've ever seen or heard about at a bachelorette party?
• Why do you think most harem anime and manga have lame male protagonists that would be considered losers and pathetic by most people?
• In Italy, how do people greet each other when they meet for the first time (e.g., on the street)? What's a good response to that greeting if you're not from Italy or don't speak Italian fluently yet?