While jumping off enough height, death arises either by the dashing of the body or by the damage of several essential internal organs. If falling down more than 100m, death should be certain and immediately. Alcohol is unadvisable, it relaxes the muscles, which may protect the internal organs if they are relaxed.
From a height of 30m there is a 90% probability of death. The longer the fall, the higher the probability of death will be. If it is over 100m on land, and 200m on water, the probability is near 100%. The fall from the Golden Gate Bridge, for example, is 74 meters, and 98 percent of jumpers  die.
- It might be helpful to take a anticoagulant to minimize the chance of surviving if the organs aren't damaged enough.
- To bring oneself to jump, it may help to count to three and jump at two, to fool oneself / the survival instinct.
- Instead of alcohol, it may be helpful to take benzodiazepines or opiates to calm down.