The inevitability of death means that you should be conservative and responsible in your youth, and take more and more risks in pursuit of pleasure and happiness as you get older.
The rationale is that at 20 you have probably 50+ years ahead of you, whereas at 60 you may only have 10-20 years left. Logically speaking, any risk of death, long-term imprisonment, or crippling injury will be far more serious if it robs you of 50+ years in your prime than 10-20 years of old age. Therefore you should not smoke, race cars on the public highway, commit crimes, engage in high risk sex, take drugs or drink to excess in your youth. Rather you should save those activities for when you are 50-60+ and don't have as long to go.
In other words, death means you should grow old disgracefully.