. . . and we know this because? Real-world experience you say?
Back in the 90s, I had the world by the balls. Hot young girlfriend, great job, best money I'd ever made, future so bright I had to wear shades.
Within two years time my best friend died, the hot girlfriend shitcanned me, and a change at corporate blew up the job.
So yeah, I tend to have low expectations that good times will ever last.