"To live, man must hold three things as the supreme and ruling values of his life: Reason--Purpose--Self-esteem. Reason, as his only tool of knowledge--Purpose, as his choice of the happiness which that tool must proceed to achieve--Self-esteem, as his inviolate certainty that his mind is competent to think and his person is worthy of happiness, which means: is worthy of living." [Ayn Rand, For the New Intellectual, p128]
Self-esteem is the belief that one is capable of achieving values, and worthy of them. Self esteem is closely tied to pride and happiness. Pride is the pursuit of moral perfection, and happiness is the long-term result of achieving values.