I can only partly imagine that kind of feelings and I'll tell you why.
There were plenty of opportunities in bitcoin. Ok, he missed one. Or two. Or three. But missing them all is something I cannot understand.
I could have bought good amounts at 200-250$ and I didn't. That's the train I've missed. But since then I've earned some more. Of course, I made other mistake too: I've sold now and then, or bought things for bitcoin.

If I look back, yeah, I probably could be kinda rich now if I wouldn't have made those mistakes. But dead inside? No. Life goes on and I hope that what I have and what I will gather will help me with an easier retirement in some more years.