I think passion goes a lot further than passion between two partners. There's also a passion for life that we all have. I think if two partners can support each other's passion for life they will not be loosing passion for each other.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~