Ian, if by "I" you mean your ego, then you're between birth and death, in the time-bound sense. If by "I" you mean the field of Unified Awareness, then "you're" beyond birth and death.
Yin is the yielding force, Yang is the action force, but neither could exist without the other. Aikido, in my opinion, is a beautiful metaphor for this- The actual power within it is from it's synergy (a condition where the total is more than the sum of it's separate parts) and not from any of it's individual components.
When Uke pushes, pulls or strikes and Shite/Nage turns, blends or receives, it's Yang/Yin. As we know, this exchange can also be reversed in different waza. But the exchange is still