Diane Vaughan said this quote

We all are secret-keepers in our intimate relationships. We keep secrets from our partners about daily encounters, former lovers, true feelings about sex, friends, in-laws, finances, personal hopes, and worries about work, health, love, and life. It may be, in fact, that keeping these secrets makes all relationships possible. If our partners knew every thought, every nuance of our selves, our relationships would run the risk of succumbing from either constant turmoil or—perhaps worse—a tedious matter-of-factness devoid of surprises. Whatever their contribution to the maintenance of our unions, secrets also contribute to their collapse.