Roughly speaking you are often best off choosing what the rational course of action is and then picking the opposite.

I consider this a symptom of poor scenario design - the availability of unpredictably optimal actions is the key technical difference (there are of course social differences) between open-ended and computer-mediated games. If the setting is incompatible with the characters' motivations, it's impossible to maintain the fiction that they're even really trying, and either the setting's incentives or the characters' motivations (or both in tandem) need revision.

Running a good open-ended game in the presence of imaginative and intelligent players is hard. You either leave lots of material unused, or rob the game of its key strength by over-constraining the set of possible actions.