It is severely forbidden to say Lushon Hura, and B”H a great deal of attention has been given to the subject. Interestingly enough usually the bad experience or knowledge that a person wants to share was something that was specifically meant for him, and often him only. E.g. a person goes somewhere and sees the place covered with garbage, everyone else that went there saw an immaculate place, two minutes before he came, H”Y had someone cover the place with garbage. And if this is not the case, it could be that the bad this person experienced or perceived was completely conjured up due to his own personal faults which he saw reflected in his surroundings, but were only subjective to his damaged site. Rabbi Nachman takes this idea to an extreme by saying that even when a matter is in fact bad, one can relate to the good in it, this will actually effect that particular matter and bend it to the good venue. So by relating it's bad projection, the person himself is the one perpetuating the bad.