Interpretations of this santayana quote?

“I have never seen much evidence of happiness in human life; but personally I cannot complain of my lot. It has been tolerable enough to allow me to be disinteresting in speculation and therefore happy in it, as musicians can be happy in music or mathematicians in mathematics. But as men, we are all sad failures. The world is a blind power, is too much for us, even for a Napoleon or a Goethe. But the same world, as an object of thought, is a wonderful theme; to understand it, virtually and mythically, as a man may, is the supreme triumph of life over life, the complete catharsis. Nonetheless, from the point of view of the animal in man, the truth remains tragic. An animal can be confident and brave only if he does not know the truth.”