A sense of life is a pre-conceptual equivalent of metaphysics, an emotional, subconsciously integrated appraisal of man and of existence. It sets the nature of a man’s emotional responses and the essence of his character.
Long before he is old enough to grasp such a concept as metaphysics, man makes choices, forms value-judgments, experiences emotions and acquires a certain implicit view of life. Every choice and value-judgment implies some estimate of himself and of the world around him—most particularly, of his capacity to deal with the world. He may draw conscious conclusions, which may be true or false; or he may remain mentally passive and merely react to events (i.e., merely feel). Whatever the case may be, his subconscious mechanism sums up his psychological activities, integrating his conclusions, reactions or evasions into an emotional sum that establishes a habitual pattern and becomes his automatic response to the world around him. What began as a series of single, discrete conclusions (or evasions) about his own particular problems, becomes a generalized feeling about existence, an implicit metaphysics with the compelling motivational power of a constant, basic emotion—an emotion which is part of all his other emotions and underlies all his experiences. This is a sense of life.
Ayn Rand, "Philosophy and Sense of Life"