As a matter of fact, Pardner, you’re right. But I ain’t yet sunk to horse stealin’. Oh, I’ve salted claims, yeah. And I’ve sold whiskey to Injuns. And once a man in Walla Walla come at me with a gun and I killed him. I can’t think of one commandment I ain’t shattered regular. I never did fancy my mother and father, let alone respect ’em or honor ’em. And I have coveted my neighbor’s wife – whenever I had a neighbor and he had a wife, mm, mmm! And I gamble and I cheat at cards, but there’s one thing I do not do. I ain’t never gulled a pardner. The one sacred thing, even to low scuff like me, is a man’s pardner. — Paint Your Wagon

Abused trust is lost trust.  There has to be a line in any relationship beyond which the relationship disappears, or one member of the duo becomes the slave of the other.  That line needs to be bright, thick, and agreed upon before any relationship moves forward from square one.  Maybe it’s making sure that your significant other knows you will never put up with violence or infidelity.  Business partners should agree that all dealings will be transparent and to a mutual benefit.

No matter what that line is, once it is crossed, then you continue with the relationship at your own risk.  Someone who will abuse your trust once is likely to do it again.