The human mind will be crushed into a prison by the weight of their own eternal existence. It is worse than being held in an a empty void for eternity. You are being held in an empty everything. The weight of everything will be always on your back, but you will not feel it.
You will experience what it is like to be given an eternal reward. The crushing existential thought that the only thing that can destroy you, destroy your beliefs, obliviate everything you think and reverse it is yourself, and the knowledge that when one deals with eternity, that this will happen is inevitable.
Heaven is worse than hell.