While happiness is best defined as a state of being content, we didn’t actually evolve to be content. We evolved to strive and to struggle and to compete, so by nature, we don’t get rewarded for being consistently happy.
Though I agree to the essential idea you expressed in the article, I feel contentment is defined a little narrow here. Contented could also mean fulfilled and satisfied even in the struggles, but could compete and struggle for becoming better. Contentment can’t be put on the same league as pleasure..