Trust is the worst thing to lose. Once it is lost, it is VERY tough to get it back. There is no quicker way to lose trust than by lying. Once a pattern of lying has been established, it becomes a matter of others simply assuming that what is said IS a lie, and when the statement turns out to be true, it comes as a surprise.
If there are enough "truths" told, trust has the CHANCE to be earned back. But the process is molasses-slow.