This reminds me of a talk by Peter Railton I attended several years ago. He described happiness as a kind of delta function: we are as happy as our difference from our set point, but we drift back to our set point if we don't keep getting new input. Increasing one's set point will make one "happier" in the way you seem to be using the word, and it's probably possible (we already treat depressed people, who have unhealthily low set points and are resistant to more customary forms of experiencing positive change in pleasure).