There are many people who strongly believe in bad luck after breaking a mirror, a black cat having crossed your way or number 13. However, there are those who ridicule such beliefs as silly superstitions that have no reasons to be taken seriously.
I feel skeptical about superstitions and will now try to explain why people believe in them. Reason number one is that many believers prefer to rely on good and bad omens rather than on themselves. Reason number two is that quite a few people want to avoid bad luck. Finally, reason number three is that certain individuals, such as students before the exam, feel insecure and superstitions help them to be more confident.
An opposite point of view is that superstitions contain some secret knowledge and can really help. Perhaps, black cats carry with them some warning signs and we should scare them off. Or, maybe, number 13 really signals bad luck to people. Another wild guess is that there might be some mysterious world behind the looking glass and we should handle it with care.
I admit that it is hard to argue with believers, everybody has the right to agree or disagree with them. I suppose black cats look scary especially in the dark and there is nothing else to them. As for number 13, thousands of lucky people have been born on this day. Regarding the mirror, it's the danger of injury that I have in mind.
In other words, I feel skeptical about superstitions and think that people believe in them for lack of knowledge about the world and due to personal insecurity.