Good and Bad Depends on One's Mouth:

Shlomo Hamelech says (Koheles 6:7): "All of a person's toil is for his mouth." This can be translated to mean that all the pain and suffering a person endures in this world is a result of improper use of the mouth. Sefer Marpeh Lason (Amud Hayirah 29.2) quotes the Shlah Hakadosh as saying that all tzaros we have faced from the time of the creation of the world were caused by the sin of lashon hara.