Fear paralyzes; sometimes we allow it to, calling it “caution”. It’s good to be cautious. Not so good to be paralyzed. Either by over-analysis OR by fear.
(Though, extreme analysis can combat fear; see Freakonomics for the statistics on child restraints…)
A good nugget from Tim Ferriss’s Four-Hour Workweek is this (paraphrased):
The thought of the “worst-case scenario” keeps us from acting, yet the worst-case scenario almost never occurs.