What are important things and advice to know that people generally aren't told about, e.g., had someone told you ‘x’ or ‘y,’ it would have saved you time, money, heartache, blood, sweat, tears, and so forth?

Personally, I never smoked cigarettes but now that I’m an old woman I can tell you every single person I know that smoked a pack or more a day has lost all of their TEETH. Also, every single person I knew that did a lot of cocaine when they were young has DIED of CANCER before they could enjoy their retirement time.