Every man has his secret sorrows which the world knows not and often times we call a man cold when he is only sad
"Ah! this beautiful world!" said Flemming, with a smile. "Indeed, I know not what to think of it. Sometimes it is all gladness and sunshine, and Heaven itself lies not far off. And then it changes suddenly; and is dark and sorrowful, and clouds shut out the sky. In the lives of the saddest of us, there are bright days like this, when we feel as if we could take the great world in our arms and kiss it. Then come the gloomy hours, when the fire will neither burn on our hearths nor in our hearts; and all without and within is dismal, cold, and dark. Believe me, every heart has its secret sorrows, which the world knows not, and oftentimes we call a man cold, when he is only sad."
-Henry Wadsworth Longfellow, Hyperion, Book III, Chapter IV