It's bad enough that Batman was paranoid about Superman being a potential threat to Earth in Batman v Superman: Dawn of Justice last year, but he was also plagued with nightmares. One of those upsetting dreams had Bruce Wayne visiting his parents' crypt, but then he was attacked by a bat-looking monster that looked like it came straight from the depths of Hell. The creature was terrifying, but an earlier concept art version looked almost equally as frightening.
Artist Patrick Tatopoulos recently posted an unused design for the bat-creature on his Instagram page, using the same situation in the movie: Bruce just trying to visit Thomas and Martha Wayne's resting place. You can compare the thing above with the final product below, but the main differences are the former being gray instead black, and the nails also appear to be much longer. Oh, and there isn't black ooze creeping out of the cracks, but I'd count that as a positive. That was just nasty. It's also worth noting that the creature, whether it looks like the concept art above or the final version, was not intended to be Man-Bat, a longtime member of Batman's rogues gallery. Still, that doesn't mean we couldn't see Dr. Kirk Langstrom transformed later down the line in the DCEU.
Batman has always been a person naturally suspicious of the world and always on edge, but the events of Batman v Superman: Dawn of Justice pushed him to new levels of paranoia. The dream involving the bat-creature was enough to jolt him awake in a cold sweat. However, it was the Knightmare that really got to him. In that scenario, Batman was a resistance fighter on an Earth that had been overrun by a rogue Superman and the forces of Apokolips, and despite his best efforts, he was captured and killed by the Man of Steel. However, the dream immediately afterwards (or was it?) of a red-clad figure charged with electricity delivering an enigmatic message suggested that this Knightmare was actually a vision of a potential future. Either way, these visions were enough to push Batman to take action against Superman by building his own armor and crafting a Kryptonite spear. I mean, maybe Bruce Wayne could have just gone to see a sleep specialist, but trying to kill a Krytponian hero as treatment works too, I suppose.