Do you really die when you say cross your heart swear to die and you do it?

The phrase "cross your heart and hope to die" is a traditional expression often used to emphasize the seriousness of a promise or secret. It is not meant to be taken literally; rather, it's a rhetorical device rather than a statement of intent. Saying it does not have any power to cause actual death. Death is a biological process and cannot be invoked by mere Words or phrases.