I think that feeling of wasted potential is often the worst part of it. There are so many examples, and some of them are heartbreaking, like the folks who were too old to have kids when they finally got out, and realized that they would never have children or grandchildren. It's awful.
I was kind of lucky, in that an opportunity in IT opened up for me just as I was coming to terms with the idea that I wouldn't be able to pursue a career as a comic book or fantasy artist. I was able to build a real career and am working towards a decent retirement, where I can draw and paint to my heart's content and not worry about pricing dog food for dinner.
My mother wasn't as lucky, she has remained a diehard PIMI and has spent 50+ years waiting for the end. She passed up a career as a nurse, and was smart enough to have done any number of things. But instead she has sat and waited for the end. What good would it do her to wake up in her mid-80s? All she has left, for the past 20ish years, is The New System. Everything that she could have accomplished? Too late. The clock did not run out on the world. It ran out on her.
There are so many stories like that.