[potatote]

I believe that it's not too bad to let negative thoughts pass through our stream of consciousness everyday. I mean, it's part of being human to have different kinds of emotion, right? The intervention is necessary ONLY IF one feels like negative thoughts are occupying too much of his/her mind space and is debilitating his/her day-to-day functions.

Other than that, we may sometimes be happy, be sad, be angry, be disgusted, be afraid and so on. Just don't linger on one for too long (know that time will help us forget) and that's a good enough approach to manage the emotional flux.