What will make one have seven years of bad luck according to the speaker?

W: Oh, no! Oh, I can’t believe I dropped that mirror. What bad luck.
M: Don’t worry, mama! I’ll pick it up for you.
W: Thanks. But you know I can just hear your grandmother’s voice saying" Now you are in for seven years of bad luck. ".
M: Why would she say that?
W: Oh, you know her, she’s very superstitious. She believes that once a mirror is broken, you can’t see yourself as a whole person in it. So something really had is going to happen to you.
M: Yes, but why? Why seven years of bad luck.
W: Well, I guess a long time ago, people thought it took seven years for the body to repair itself, so I guess it would take seven years to fix a broken body.
M: Seven years is a really long time. I guess I’m glad I didn’t drop that mirror.
W: Oh?
M: No, mama, I’m only kidding. I mean you don’t really believe in that stuff, do you?