In my law enforcement career I investigated a little over 100 fatal accidents. From that, I learned these absolute truths, in no particular order:
Speed kills. At speeds over 70-80mph you are exceeding the survivability of the human body. Your car, your safety gear, etc. cannot be counted on to save you.
Don’t drink and drive. Driving requires you to be able to divide you attention and observe several things simultaneously. Being drunk makes dividing your attention impossible. It’s not something a person can learn to cope with or overcome.
Seatbelts save lives. Almost everyone I have seen die in a car crash would have survived if they had a seat belt on.