I will speak from my experience. When I was younger, I considered myself very smart, and I was pretty unhappy. As I grew, I met people much smarter than me; I stopped seeing myself as "the smart" one, and now I am pretty happy. It's not that I became happier because I became less smart; I became happier when I stopped thinking my value was based on my intelligence, so I stopped trying to be recognized by my intellect…
i still, deep down, identify as being "smart". i don't like being wrong, and it's my go-to ego lick at work, "well bad thing x may have happened, but at least I'm still valued for being smart". it was my label in high school that i've never quite shed.
obviously now i have so many more facets - father, husband, leader, writer/reader. Smartness is just raw horsepower, it's what you do with it that matters. And there's lots of kinds of "smarts". As an example, my wife wasn't the traditional "book smart" but she's emotionally & street smart - knows how to get things done, how to think on her feet, etc.
but still despite that increased richness from life experience, I'm still "smart" and hold on to it