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.