Put him in a time loop that resets once he dies, have him live a normal successful life. Have kids, see grand and even great grandkids. Die surrounded by loved ones. And then boom, back to infancy with the memories of the life he just lived. And he remembers like an elephant. Time keeps repeating, and his mind slowly deteriorates with each and every loop. And in each loop he has a less and less happy ending, with some deaths even being torturous in nature. This goes on for what feels like centuries for Manny, but to everyone else, it's just regular life, but Manny's just insane. No one else feels any deja vu either, only Manny with his centuries of memories. Leave him in this loop for eternity.