Both, though in my case, natural causes means mortal injuries. Yes, Time Lords may choose not to regenerate, but that doesn't always work, because sometimes our bodies have a mind of its own and will decide to pop up alive. Also, we only have twelve shots at it, after which our energy is depleted.
You're probably the first person I've traveled with that's been okay with that.
I'm a professor at Abacus Institute, so obviously I'm not very creative, either. Although, I have picked up painting with spray paints on the side of the road, and sometimes I play the guitar in the city's underground.