Can We Think About Our Own Death?

Is there a limit how long we can ponder our own death? Do our brains switch away from this automatically? I remember reading on the net that our human brains are wired in such a way that we can contemplate
our own death for only a brief time before the brain switches to another topic. I have not been able to find that source
again. Two questions. Can anyone else find it? Can anyone speak to the brain wiring / death topic avoidance issue?