Been debt-free, employable I have gone through the painful experience of failing. It isn't about your mechanical abilities being challenged, i.e. skills and ability to pay the bills, it's more about the astounding realization that "I cannot make it" thing. To be disappointed with yourself is much more painful than slavery IMO and is usually the cause of depression.
The very first startup I was in (as an early employee) went IPO in the late 90s. My next startup (where I was a founder) crashed and burned in the tech bust that followed. The crash was beyond my control, however failure was incredibly hard to deal with for the reason you mentioned.
I did the obvious thing, got a real job, saved cash etc. Things have obviously changed dramatically since then in terms of ease of starting one's own project, so I've been plugging away at mine for a while.
I have to admit though that I do find myself thinking like "Bob" sometimes because I want desperately to avoid another f-up. I've gotten around it by having a key team of advisers/mentors that have done startups successfully. I challenge their opinions sometimes, but generally listen to what they say.
Its also very easy to over-analyze something until you don't know what's up or down.
