Because it's always black and white.
Only one, but they have to turn it on and off 50 times before they're sure it's fixed.
Because when he turns his girlfriend on he has to turn her off again three times.
OCD, OCD, OCD. Wait the last time didn't feel right. OCD, OCD, OCD. Wait, the second time didn't feel right. OCD, OCD, OCD. Wait...
Seven. It *has* to be seven.