Belief in luck is generally regarded as a form of magical thinking. However, there is evidence that people who believe themselves to have good luck are more able to take advantage of fortunate chance events in their lives, and to compensate for unfortunate chance events in their lives, than people who believe that they have bad luck. This appears to be the result of positive thinking altering their responses to these events.
If "good" and "bad" events occur at random to everyone, believers in good luck will experience a net gain in their fortunes, and vice versa for believers in bad luck. This is clearly likely to be self-reinforcing. Thus, although untrue, a belief in good luck may actually be an adaptive meme.
Most cultures consider some numbers to be lucky or unlucky.