A person can imagine their own funeral only by quietly giving themselves a place to watch it.

You cannot picture your own absence without smuggling yourself in as the observer. The scene needs someone to see it, so imagining being gone quietly requires you to be present, which is why the exercise never quite delivers what it promises. The mind has no way of representing its own non-existence.

That limit is worth knowing rather than fighting. What the exercise can do is show you what you would want said and by whom, which is information about the present. If a name comes up that you have not spoken to in a year, that is not a thought about death; it is a thought about this month.