Things go bump in the night. Shadows play tricks on your imagination. Some of the most fearsome hunters in the animal kingdom are nocturnal. All of those things are valid reasons to be afraid of the dark, but mine goes a little bit farther.
I can't fucking see in the dark. I have terrible night vision. Stumbling around the house with the lights off is just an exercise in seeing how many things I can run into before I wake my wife and kid. Driving at night is taking my life and the lives of everyone around me in my hands as I try to aim between the headlights zooming past on the left and the yawning black abyss on the right and hope for the best. If it's raining too then I might as well drive with my eyes closed.
So yeah, I'm not so comfortable in the dark.