Like that bad after-taste, some things never go away. Even if trivial, they keep nagging you, niggling at the back of your mind. Wisdom would be in letting go, but you prefer to hang on. So the fault, then, is within. The ability to forget, let go and move on is unfortunately not a long-lasting trait. It needs to be learned and re-learned each time, with every new undesirable situation that arises. Of course, we'd all be sadhus if we could automate this reaction each time, I guess that's what makes us mere mortal. One of the basic principles of yoga is detatchment, something I have never come to adopt. It seems to take the fun out of life. I would never want to be completely detatched, to stop things from bothering me, because then what would be the fun? I'd much rather have highs and lows, disappointments and upsets, pick up and move on, bruised and wiser.
Ignore me, I'm rambling.