Life does not reward intelligence; it tends to reward focus and persistence. Smart people occasionally do really dumb things. Smart people occasionally do self-defeating things which negate their own smartness.
Being self-critical: Smart people can see through themselves. They can keep their ego aside and see their flaws and shortcomings. Perhaps they lack social empathy or have a slurry speech. Unlike the commonly perceived trait of intelligence, smart people may be slow in processing information or they may be less creative than they expect from themselves. By accepting their shortcomings, smart people are often unsatisfied with a part of themselves, especially the part which is inherently present in them and can’t be changed much.
Seeing the truth: Smart people know that there is no ultimate justice- that this is not a fair world we are living in. You can see people condemning and criticising others far more than applauding and encouraging them. Smart people can more easily see the flaws in people and are more likely to remember them. Of course, they also see positive qualities like love and generosity, but they reject the idea that humans are predominantly “good”. Smart people know that the media, television, and our society are often pretentious about showing goodness. Seeing the truth is an ugly realisation for smart people.
Stupidity: Since smart people are smart, they have to deal with a great deal of stupidity in their daily life- stupidity not because of lack of knowledge or intellect, but stupidity because of how self-righteous, arrogant, and rigid people are.
: One of the characteristics of smart people is their quest for knowledge. It may seem as a very noble quest from the outside, but on the inside, it gets increasingly painful. The more the smart people know, the more they know how little they know. Smart people are also open to criticism and contradictory opinions. So when someone finds and convinces them about a flaw in their idea which they had been believing in for years, they think for a moment whether most of the things that they believe in are actually false. Smart people are really bothered by the limitations of the knowledge.
Uncertainty: Smart people don’t think in absolute terms- be it morality, societal norms, or the universe. They can form two sides and carry out arguments within their heads without a significant role of their cognitive bias. Several times, they realise that even the logical approach of reasoning can yield conflicting viewpoints. They realise that some things are uncertain and are neither falsifiable nor provable. People find comfort in drawing lines and sticking labels- theist, atheist, socialist, conservative, liberal, feminist, INTP, etc. Since smart people don’t think in absolute terms, they don’t like to cage themselves in a pre-labeled box of ideas. They are reluctant in choosing sides when they acknowledge the uncertainty. Uncertainty gives a sense of incompleteness which doesn’t bring peace to the mind.