You should not fear "bad signs" or superstitious mumbo jumbo. We should all know better than to fear certain numbers (like the number thirteen here in the US) or actions (walking under a ladder) that are nothing more than silly superstitions. But it’s fascinating to learn where those superstitions came from – hint a lot of them come from religion (like the number thirteen!). Knowing where these myths come from makes it easier to dismiss them, see them as illogical beliefs, and know that they are not worth taking seriously.
You can see a full lesson on the topic here: http://ed.ted.com/lessons/where-do-superstitions-come-from-stuart-vyse