A Psychiatrist is the best person in the world to tell us if we are vulnerable to such situations. However, a Psychiatrist can treat only sick persons. Should I wait till I get sick or run into trouble to get help. Should I be stopping buses and cars to know that I am struggling with thoughts and feelings that could harm me and my life. They themselves can not believe that they did it.
Actions are physical manifestation of thoughts and feelings.
So also is speech that expresses our thoughts. If we can assure that our mind is okay then the rest would be fine as well. The Psalmist who penned Psalm 139 has known this truth. That is why he cries to God to search his heart. He also knows that the way to sorrow is not outside him but right within him, in his feelings.