Crossing fingers, black cats, rabbit's feet, broken mirrors, they are all harmless superstitions that people believe in that help them through their day. People use superstitions like crossing their fingers or saying a certain chant or phrase to prepare themselves for difficult tasks they feel they can't do by themselves. Athletes and musicians also rely on their superstitious beliefs—like lucky clothing articles, or some routine before a performance—because they think it makes them play better. Superstition is a safety net for people when the other things they rely on fail. They use their superstitions to help them in life.
Superstitions can be beneficial to the people who have them because they can make the people act like they would not normally act whether they want to or not. Even though they think the superstition is causing them to do better, it is just their new confidence or experience that is making them do better. Without the superstition though, the person might be thinking about how they don't have their extra edge, which would cause them to perform worse. How do people get caught up in superstitions so easily?
When an athlete, or anyone for that matter, attributes something they do that is beneficial to them to be caused by some superstitious act or object, they fall into the circular reasoning fallacy described by Michael Shermer. He says “[Circular reasoning] occurs when the conclusion or claim is merely a restatement of one of the premises”. Take a lucky sock for example, if someone asked an athlete why the sock was lucky, they would say it is because it helps them to play better. Then if asked why it makes them play better, they would say it is because it is lucky. Notice how the conclusion, the sock is lucky, is derived from the premise that the sock is lucky. Circular reasoning like this is behind many of the superstitious practices today, but some are based on religion or culture.