A method of training a trainee includes a sensor configured to measure at least one biological indicator of stress in the trainee. The method includes presenting a training segment in the simulation while monitoring inputs from the trainee. Data is read from the sensor and an instantaneous stress level of the trainee is calculated from the data. If the instantaneous stress level greater than a predetermined value, a stress-change feature is selected that will reduce stress and applying the stress-change feature to the training segment, thereby reducing complexity of the training segment for reducing the instantaneous stress of the trainee. for example, the stress-change feature is changing the weather, adding/removing bad drivers, adding/removing pedestrians, etc.