Please help! what is the most effective poison?

I won't tell you: If you are thinking of harming yourself, get with your personal physician -- these are thoughts you should not be having, and you can find something better than death. If you feel you will lose control, call 911 or go to the emergency room. The vast majority of people who attempt to hurt themselves ; fail are glad, one year later, that they failed. Would-be homicidal poisoners usually get caught.