For my sake
According to Lara, I didn't literally come out of her womb, my ancestor was. What she meant by I lived and died, she was talking about the core that was hidden within me. That core was akin to a bubble and within it was a concentrated power and knowledge of the Bloodfang clan and Lara. It was passed down from generation to generation until it could find a body, a suitable host.
After centuries, the core had finally had found its perfect host, and that was me. If it wasn't for me, my children would have to bear the responsibility. If none of my children could handle the core, then their children would.
A never-ending cycle that would only stop until a suitable host was born. Once this happened, the core would stop in that person, in me. Whether I live or die, my core would stop in this body.