The Grand Cross is, indeed, a very rare and very powerful configuration in an individual’s birth chart. It is an intense and potentially stressful concentration of energy which may involve more than the basic 4 luminaries/planets. The theory goes that the individual with such a configuration will be driven by the intense flow of energy to achieve remarkable success in life or that they will collapse under the pressure. Having a Grand Cross configuration would be extremely difficult at times of heavy, malefic transits and progressions. If the aspects between the natal planets involved were particularly tight, then a huge amount of negative energy would be triggered all at once, affecting many areas of life and thus making life rather difficult to cope with for a time.