Many times, we have good intentions. But influenced by our lower emotions and thoughts, our intentions turn into bad. And that is why great teachers have always focused on purification. Greater the internal purification is, greater is the control of SELF is over managing our lower nature. After all, a knife can be used by skillful surgeon to save the life of a patient or by thief to rob and kill an innocent. Instrument is same, what differs is the INTENTIONS.