My mom had lots of superstitions she learned from her mother. She said she didn't really believe them, but I think she did. The only one that seems to have stuck with me is not giving knives and scissors as gifts because it will cause the relationship to be severed. I don't believe it, but I don't do it. Don't know why. Actually, now that I think of it, we gave our son and his wife some flatware for a wedding present, and I guess that didn't count because the knives were not sharp, except maybe the steak knives... Actually, that was more than 15 years ago, and so for no problem!
I, too, have had black cats, and the only bad luck is that they didn't live forever. We have renamed every dog we've ever owned because we get them from shelters, and there's no way to know their previous names. One dog seemed hard to name. We asked her over and over, "What's your name?" One time she responded "Rooo-rooo!" So we named her Roux.