Many superstitious beliefs have a basis in practicality and logic, if not exact science. They were often practical solutions to something unsafe and eventually turned into superstitions with bad luck as the result. For example, opening an umbrella indoors is thought to be bad luck, but in Victorian England, unfurling a large metal spoke umbrella inside was easily a hazard to small children or fragile items.
Another common superstition that does have basis in magical beliefs is that of walking beneath a ladder. The belief, which comes from Egyptian culture, is that a ladder leaning against a wall forms a triangle and the triangle represented their gods. However, avoiding walking beneath a ladder also has plenty of practical application, as the person walking beneath it could easily knock it down.
Beginner's luck has a certain amount of scientific validity as it seems to reinforce the idea that gambling is ultimately about luck, and that professional gamblers spend so much time analyzing their choices that they end up losing anyway. Whereas the beginner is usually playing for fun and not putting effort into winning. A similar psychological superstition is bad luck coming in threes. After one piece of bad luck happens, the victim is likely to look harder for the next two pieces of bad luck.