I've seen similar - Them: "You're too pessimistic" vs. Me: "You haven't thought this all the way through".
There's a balance to be struck though, because often worrying too much about things that don't happen or saying "I told you so" when they do only really serves to annoy people.
There is indeed a balance, because opportunities tend to have time limits. Thinking things through for too long to arrive at a sure and optimal way of doing something might mean failing to take the opportunity you had to do it at all.
Thinking things through isn't necessarily pessimistic. When I have a contingency plan already in mind, I worry less about the event actually happening.
It sort of makes sense in an engineering/programming context, but life in general doesn't really lend itself to that level of control.
Did you ever try thinking about how they might turn out for the best instead to compare results? Energy follows thought, the more you focus on it the more likely it is to happen from my experience. And the only place and time you're ever going to stop failure from happening is here and now using up to date local knowledge.
There's a balance to be struck though, because often worrying too much about things that don't happen or saying "I told you so" when they do only really serves to annoy people.