If i hadn't jerked and woke myself up,i would have died. Is this true?

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Sometimes when I am sleeping I will jerk and wake myself up. My friends say that i am dreaming about falling,and that if i hadn't jerked and woke myself up i would have died. Is this true? I mean,the only thing i could fall of when i am sleeping is my bed. But i don't believe i could die. Is this an old wise tail?