The legacy you leave behind is the whole of who you are: the sum of the parts.
Subconciously you live the past of someone else's life. The clothes you choose, the breakfast you eat, the way you travel: these parts were travelled by others and now by you. You are influenced by the past with each and every moment. You are experiencing someone's legacy, known or unknown to you.
And then there are the magical moments of conscious choice. The moments where you choose to live a moment in dedication to your spouse, your friend, your mother, your father, your brother, your sister, your child. You not only continue their legacy, you contribute to your own.
This is immortality. We live it each and every day with the small choices we make. We live it each and every day with the large choices we make. We live it each and every day with our subconcious reactions, with our personalities, with our involvement, with our indifference. We are the sum of our parts, but those parts are rich with legacy. And the person we were, are, and will be: you are immortal.