It doesn't matter if you've been with your significant other for 2 days, 2 weeks, or 2 years. Without trust, a relationship can't survive. Like loyalty, respect, communication, and honesty, it is one of the essential ingredients of a healthy, long-lasting relationship. Is it any wonder that infidelity wrecks a relationship like nothing else? Imagine how difficult it is to confide in someone who took your trust and sliced and diced it by cheating on you. There aren't many other things a partner can do that are nearly as deplorable. The same can be said for a friend who steals from you or a sibling who talks behind your back. They can make repeated assurances that they'll never do it again, but our gut tells us to guard ourselves against the prospect of being subject to similar behavior in the future (whether from that person or anyone else). I'm not saying you should never give someone another chance -- only to be careful not to allow them to run ro...