I would throw salt over my shoulder but...

I really don't understand all that superstition stuff. Where did it come from? I mean, I suppose the horse shoe thing has some kind of logic behind it - the luck falls out-, but spilling salt? How is that bad luck? And how would throwing salt over your shoulder going to change that? Was there an insane outbreak of falls, bone breaks and deaths after horrible salt spills? Did someone say that they too had spilt salt, but for some reason threw some behind their shoulder afterwards and they were fine?
And walking under a ladder. Was some great power in the world just incredibly paranoid about ladders? I just don't see the sense. Some people really do have collections of good luck charms, but I don't have the time or energy. I mean I did have a pretty bad fall after spilling some salt at breakfast, walking under my dads ladder and holding a horse shoe the wrong way up after it randomly fell out of the sky, but I'm convinced it was a coincidence.
Cat xx