Trust is a very important thing in our lives. And the ability to keep secrets is a big part of what inspires trust in others. This Maxim could also be phrased as “Keep secrets”. But the importance of those secrets is not only to the person whose secrets they are but to the people who are asked to keep them. Being asked to keep a secret is often a measure of how close you are to a person. And even an inadvertent slip can cause damage to relationships that can take years to heal.
There are almost never any good reasons to reveal a secret unless you are guarding the secret of a crime that has been committed, and even then police must maintain some of those secrets for investigative purposes. The only reason is to save a life or to keep someone from harm, and unless there is an imminent danger of death or bodily harm, even then the keeping of a secret must be weighed against the possibility that telling it would cause more harm than good. In most cases, those needs do not exist so trust must be maintained. It is what helps keep our relationships strong both between mortals and between us and the Gods.