What does "living the first line of my obituary" mean here?

I came across a new phrase while reading an appeal letter from Wikipedia programmer here.

Excerpt:

I feel like I’m living the first line of my obituary.

..........

What does "living the first line of my obituary" mean in this context?

I would want my obituary to reflect the parts of my life of which I'm most proud. I expect the author feels the same. So, with these words, Brandon intimates his sense of pride in working at the Wikimedia Foundation.

It means the most important thing you will do in your life. It is a reference to the TV program The West Wing when C.J. said, referring to her job as the chief of staff:

"You think I'm not aware that I'm living the first line of my obituary right now?"

It means that it is the most important thing for which you will be remembered which is how obituaries begin. Whether it is the most important thing you will do in your life is uncertain but it is what you'll be remembered for.