Emotions by themselves only last 3 - 4 seconds. It's the negative thoughts that we feed the emotions with, that makes them last longer. Any experience of any emotion is always valid, never wrong or bad. The negative emotions are simply signs to us that there is a problem, that we need to do something to calm the emotion down a bit (like deep, diaphramatic breathing), to be able to think about what the problem is and how to solve it, and to finally take action to solve it.