Hedonic threadmill: it's the hypothesis that we tend to a baseline level of happiness and on average, after some time, people who win the lottery are as happy (or unhappy) as people who go bankrupt.
Look at us, we are apes, barely out of trees. We were fighting predators and cold and diseases that no longer exist. Just by being alive, we are the winners of millions of years of genetic lottery, evolution, fights, love and ingenuity.
We have access to most of human knowledge through devices that fit in our pockets, can visit other countries that were legendary to our forefathers, instead of hunting wild beasts we have satellites that guide us step by step to the nearest McDonald's.
Imagine having a time machine using it to travel a few generation back, imagine describing our life to our grand-grandparents, seeing their eyes grow wide; imagine, at the end, telling them how ennui got to us and we can no longer find meaning in our life.