That seems like a really odd point to challenge, especially because he set the bar as "not out on the street with glazed-over eyes wondering what could've been." I mean, I kind of regret passing on a Google job in ~2001 to continue with an ultimately-doomed startup. I also regret not spending $10k on AAPL stock back then. I'm still quite happy with my life to date.
If you could get into YC in 2008, you could almost certainly get one of any number of great jobs in the Bay Area, and could easily found a startup again (even with YC; depending on how exactly you left, it might be a positive).
Sure, I don't question the fact that you could make a series of horrible decisions, regret them and then still later on in life be quite happy, despite those earlier failures. That doesn't make the original decision to drop out of YC a good idea. I would think, I might be wrong, you should just make it work and not drop out. You should do whatever it takes to make it work.
And I mean... to paint a little sunshine here, there are also probably plenty of times where we all have made the right decision and it had the best possible outcome in the scenario.
If you could get into YC in 2008, you could almost certainly get one of any number of great jobs in the Bay Area, and could easily found a startup again (even with YC; depending on how exactly you left, it might be a positive).