You can know a lot and still be stupid.
After some point, working harder makes achieving the goal harder or even impossible.
Most people master the art of wasting a life.
Plants are more courageous than almost all human beings: an orange tree would rather die than produce lemons, whereas instead of dying the average person would rather be someone they are not.
Some people will insult your intelligence by suddenly being nice or nicer to you once you make it … or they think you have.
One of the most common and most dangerous misbeliefs is that it is impossible for someone to be stupid just because they are a doctor or a lawyer.