Well, it's basically that the afterlife is greater than the sum of your own experience. Imagine if there were no outside and when one died they were trapped within the breadth of their own experience, the boundary of their soul so to speak - it would be impossible to relive/recall anything worse than what had been experienced in life or that could be imagined as an extension of that, even with perfect recall.
What was earthly anguish compared what awaited them? Singular. Ephemeral. Little more than a bauble laid upon the monumental steps of the wretchedness to come.
Torment, pain and anguish are nothing but meanings, they have no external existence in our world.
In the Earwaverse, however, the IF is proof positive that these things have an actual existence beyond individual interpretation.