I could be wrong, but I've come to believe that grit (http://bradt.ca/grit-scale.html) is everything. Because if you don't have revenues or momentum to start, it is grit that will get you there. Those without high grit will quit prematurely.
I seem to be in the upper quartile that is statistically likely to have what it takes to stick it out, but it feels far from certain. Perhaps it provided a slight boost in self-confidence.
In any case, thanks for bringing this up. It ties in nicely with the 'Drunkard's Walk' (cf. Mlodinov) randomness/perseverance traits that seem to increase the probability of achieving one's goals.