That would be hazardous... If you went back in time to harvest your kidneys in the past, wouldn't that mean you'd have no kidneys in the future i.e. the time when you leave to get the kidneys? Plus, since you can't actually change time, if it was your "destiny" to go back in time and harvest your kidneys the whole time, you wouldn't have any to harvest in the first place because your future self would have already harvested them. Think about that.
No, each movement creates a split timeline. So there'll be a hundred timelines where you don't have kidneys, but the time traveling you from the original timeline will continue to. Y'know?