The death knell

Some months after you've become 30 years old, you will have a "death knell": You will one day stand up, and a few seconds later your legs will behave as if they were dead: They will give way, sending you helplessly falling. This is what's called "the death knell", signalling that your body has activated its "dying process". After that, it will slowly begin to deteriorate (age) until you die.

Do you have any tips to avoid this from happening (except for never standing up)?

Exercise. If your body is fit it will deteriorate slower.