That's OK; it's not as if it's off topic to talk about yourself after I talk about me! Comparing notes is a perfectly reasonable response to a post like this. :-)

Yes, you could be right. My brain is an irreplaceable part of me, but one can always find somewhere else to live, so threats to the former are more scary.

(Though if irreplaceability was the criterion, illness worries ought to be fairly high on the list too: my body is as irreplaceable as my brain. But I suppose the thing about illnesses of the body is that one can at least live with them, usually; it would make my life more inconvenient to have to live it out of a wheelchair or using dictation software, but it wouldn't stop me being me. Which is back to your point, I think.)

My brain is an irreplaceable part of me, but one can always find somewhere else to live, so threats to the former are more scary.

Except that your brain has altered itself over the last ten years. You're not the person you were at college, you're just similar to him, and you're certainly very much unlike the person you were as a five year-old. So you're only the you you are now.