Law #1: How people perform correlates to how situations occur to them.
In short, if your perception of a person is that she is decent, then, you’ll treat her well. On the other hand, if you get burned by a different coworker, you will treat him with suspicion and a lack of trust. And the longer you keep from clearing the air, the more that person’s every behavior will support your suspicion as untrustworthy. You begin to interpret what someone really means even when they say “hello.” In essence, you get “stuck” in a negative loop.