Happiness is not viewed as a zero-sum prospect. The more skillful one becomes, the wider the happiness spread by one’s skill, and the more blurred the lines originally drawn by the categories of objectification between self and others.

"In this process of self cross-examination, the perception of self is not the prime focus of inquiry. Instead, the questions shift the focus from concern for self to concern for mastering the principle of cause and effect as it governs the results of actions.

At the same time, the questions help blur the line between concern for one’s own happiness and concern for the happiness of others. MN 61 recommends avoiding not only actions that would lead to self-affliction, but also those that would lead to the affliction of others, or of both. The qualities encouraged by the inquiry in AN 10:51 — being “uncovetous, without thoughts of ill will, free of sloth & drowsiness, not restless, gone beyond uncertainty, not angry, with unsoiled thoughts, with [one’s] body unaroused, with persistence aroused, & concentrated” — benefit not only the person practicing but also all the people with whom he or she comes into contact. The same holds true for the practices of generosity and virtue, on which the practice of meditation is based. Thus happiness is not viewed as a zero-sum prospect. The more skillful one becomes, the wider the happiness spread by one’s skill, and the more blurred the lines originally drawn by the categories of objectification between self and others."

~ Thanissaro Bhikkhu "Skill in Questions: How the Buddha Taught"