That is partly a question of scale: one lucky break by a smaller firm could double its reserves, but barely register at one of the majors.

ECONOMIST: Oil companies: Improving their fieldcraft | The

This question was addressed in a large-scale project by Gretchen Rubin who tried to increase her happiness over the course of a year by setting herself specific goals that covered, among other areas, marriage, work, leisure, parenthood, friendship, money and so on.

FORBES: Happiness Is Hard Work