I do not think it is so much about bearing a grudge more so than trying to heal from such heartbreak. Think about it, you love someone, you watch them make mistakes with other guys, you stand by and support (which by the way is something a good partner should do), you believe that that one you love has finally seen you being there all along and then BAM, nope. That is not a grudge, that is the destruction of one's self-esteem and emotional well being. Having that done to you can totally affect and or change your psyche for the rest of your life in some cases. It just goes to show that you should be careful with those that entrust their heart to you because you can destroy them with a few simple words. I speak from experience, on this. My ex-wife did this to me, not the same I grant that. But three years on from a divorce where she walked away from the marriage, gave no reason, and is remarried now in MY old house....I do not hold a grudge toward her, in fact I have no feeling toward HER at all. But my self worth is non-existent. When someone you love tosses you out like a sack of rubbish, its very hard to get the confidence back to even attempt to date, deal with rejection and even try to have a meaningful relationship with someone.