When the traffic light is red you are aware that a car might comes rushing in. So you are extra careful and always check the street before you actual cross the street. But one the other hand if you have green light and think you are good to go, it seems to be very likely that you just walk over the street without even taking a glance. There is still the danger of a car/cyclist, however, that may run a red light. Not looking could thus seriously be harmful.
So to put it in a more general context. Does expecting to be in a safe situation elicit or allow unsafe behavior?