It's a very interesting thought. The problem may be that there aren't really anyone in the vicinity of entrepreneurs that have an interest in saying that it probably won't work out: Investors lose their money, partners lose their partnerships, etc. And friends often tell you you're doing great in an attempt to spur you on.

It might be possible to set up some system that you can judge yourself by. Maybe a quiz that you can take every month that is developed by psychologists, entrepreneurs, and VC's with questions on your progress, motivation, financials, etc. Your score reflects your chances of success, and you can track it from month to month. That way you will see more clearly whether things are going well or to hell. It would be like with small children: If they are your own you don't notice how quickly they grow because you see them every day. People that only see them every month notice right away.