If sensual pleasure cannot provide happiness, how can we develop this desirable state?
The Buddha taught that happiness arises as the natural outcome of meritorious deeds. He said (It 22; 14-15):
This is an expression denoting happiness, what is desirable, wished for, dear, and agreeable . . . I know full well, monks, that for a long time I experienced desirable, wished for, dear, and agreeable results from often performing meritorious deeds.
I flinched when I read this. Hobbled as I am by a rationalist worldview, any mention of merit makes my skin crawl. (And, of course, Bodhidharma bluntly rejected the notion that action produces merit.)
But after the twitching stopped, I realized that the Buddha was not recommending action with the intention of creating merit. Rather, he was simply pointing out that certain actions produce certain effects. And the effects of meritorious actions include happiness.
So we might ask: What actions produce meritorious results? In AN 8:39; IV 24504, the Buddha says:
There are, O monks, eight streams of merit, streams of the wholesome, nourishments of happiness, that are heavenly, ripening in happiness, conducive to heaven, and that lead to whatever is wished for, loved, and agreeable, to one's welfare and happiness.
What are the eight?
The Buddha goes on to say (paraphrasing, here) that the Three Refuges* and the Five Precepts** comprise the eight streams. In short, the Buddha observes that refuge and precepts produce happiness.
We shouldn't be surprised at this, of course. When we enter the path, we express our intention to turn away from the self-centered life.
This intention, married with responsible action, ripens in happiness.
*In this passage of the Pali Canon, the Buddha defines the Three Refuges as going for "refuge to the Buddha . . . refuge to the Dhamma . . . [and] refuge to the Sangha."
** In the same passage, the Buddha defines the Five Precepts as, "[giving] up the destruction of life . . . [giving] up the taking of what is not given . . . [giving] up sexual misconduct . . . [giving] false speech . . . [giving] up wines, liquors, and intoxicants."