Psychiatrists will tell us, while there is certainly a biologic component of our biases in dealing with others, ultimately, we chose to be happy or sad. People have thought about this a long time. John Milton published "Paradise Lost" in 1667 and wrote, “A mind not to be changed by place or time. The mind is its own place, and in itself Can make a heav'n of hell, a hell of heav'n.”
I have faced my own demons -- many of us have -- it is part of the human condition -- and I hope fewer are running away as I age.