Why am i not scared to die during the day, but at night i am?

During the day im the bravest person ever i dont care if i die, but then night rolls around, and i think about death and i get get scared im not suicidal, i luv my life.Icould care less about dieing during the day but at night im scared shitless this happens more right when i go to bed. if you know what this is called please name it.