The Passion is the step into the second decade of the Major Arcana, the point
where the journey into the inner depth begins. In other decks, this trump is called
'The Power', a symbol for the mastery of our own animal side. Crowley named the card
'Lust' - and most people don't really think of mastering their inner animal, but
enjoy it full tilt...
In a combination of both, the animal side shouldn't be 'mastered' in the meaning of 'surpressed', nor should it be let out to 'romp around'. It should not be ignored, but accepted as a natural part of oneself. In that manner, one will not only be able to profit from its instinctive natural power, but also to save the power needed to 'master' it.
The Passion implies vitality, energy and power. The card tells us to use these riches. In most aspects of life, an endeavor will have much more success when passion is put into it.
Drive: Energy, passion, charisma, joy of life
Light: Power, vitality, unconditional devotion
Shadow: Weakness, insatisfaction, depression