While my intelligence is ~ constant, my levels of happiness fluctuated during my life and now, at 48, I am maybe twice as happy as I was at 24. There is definitely an upward trend with me...
During the same period, I also absorbed a lot of information, including some ghastly one. And yet my overall feeling of well-being improved.
IDK what happened, I can at best describe it as if "someone slowly changed the lens I am using to view the world for a less cloudy one".
Maybe some sort of hormonal development. It seems to be outside my will, though. Just happened.
I think what you're describing is wisdom, as described in the Serenity Prayer:
"God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference."
Oh, that would be nice! Thank you.