Re: one bad thing in the world that you think
Precaution is always better than cure. Life is too short to learn everything by going through bad and then good experiences oneself . It is always better to learn from the experiences of others (whom we trust) when they advice / warn us.
Besides, it is good to learn from past mistakes and move on, but without repentance of past sins and seeking forgiveness of Allah, sins won't wash away.
There is nothing wrong in being bothered by bad because that would encourage us to raise our voice against it, or find some solution to that negativity which might be effecting the lives of other human beings.