Our worst memories are always very powerful, partly because we go over and over, reliving them, making their image strong. We re-experience the emotions, sensations and often tell our story to others, ensuring these images are seared into our brains. Try locking in the best events with just as much intensity. Recall exactly what happened, how you felt and make the images as colourful as you can. Turn up the techni-colour every time you remember a good experience. Make the bad images more bland and grey so they have less control over you.