I agree that experiencing the "negative" emotions over a long period of time can be harmful, stressful, etc. Having said that, the concept I am suggesting is that anger, hate, resentment, lust, vengefulness... some of these emotions have ironically extracted the best out of people. For instance, take a look at art - the tortured artist (Van Gogh), the self hating rockstar (Kurt Kubain), the alien junkie (David Bowie)... Suffering and pain creates beauty too, oftentimes more so than feeling happy and grateful.
Sure, it comes at a cost as the person is living in a constant chemical storm, but hey, for every action in life there is a reaction.
For times when I will be of need to ease the negativity off my soul I will try out your trick, thanks for that. :-)