It's something I did to myself. [in the most literal way possible.] I could have asked for help, but I did not. I was too proud, and it killed me.

[his expression pinches for a moment.]

Or... whatever the timeline nonsense here is. I'm alive here, but have been deactivated back home for centuries from-- Optimus's perspective. Possibly another universe entirely. I do not think about any of this; too much of a processorache.