Venom is tense while Eddie sleeps. Without sleep, humans die.They need sleep, they can’t survive without it, but sleeping makes surviving a lot harder, too. Venom had watched documentaries, to know exactly why humans needed sleep and what happened while they slept and why their brains would do all the stupid things they did while sleeping, so he knew all about sleeping.
His conclusion was that sleeping was the stupidest thing humans had ever evolved to do.
When humans sleep, they dream. They sometimes dream vivid dreams. Sometimes violent or scary ones. To keep from acting out these dreams and accidentally hurting themselves, the human brain purposefully shuts down the muscles, forces the human to be paralyzed for the entire night. Then, after a job well-done, the brain itself shuts down to sleep. The human is paralyzed, and completely defenceless. Humans cannot protect themselves while they are asleep. Eddie cannot protect himself.
That is why Venom worries, why he hovers all night long. Eddie is defenceless, worse than the tiniest, puniest insect. At least a bug could try to run away when it sensed the danger. Eddie’s brain is not awake to sense the danger, and even if it was, Eddie’s muscles would be paralyzed. While he’s asleep, Eddie cannot sense danger, much less run away or try to fight it. So Venom remains vigilant. He hovers over Eddie, never tired, never sleeping, listening and watching for anything that might try to harm Eddie while he’s paralyzed by this stupid, necessary thing the brain does to keep itself alive.