People may follow a manual to achieve safety (Safety - I). On the other hand, it has been proposed in recent years that people sometimes respond flexibly to situations in order to achieve safety (Safety - II). Both modes (Safety - I and Safety - II) should be used mutually ; therefore, one strategy is to apply the Safety - I mode when the fluctuation of conditions is below a certain level and to apply the Safety - II mode when it is above that level. In this research, in order to clarify the level of situation fluctuation at which it is appropriate to switch modes from Safety - I to Safety - II, we conducted a simulator experiment involving a fire-extinguishing activity. As a result, it was revealed that people adopted resilient behavior when the situation fluctuation exceeded a certain level and resilient behavior led to success when the fluctuation was not too large or too small.