Our sages have said: "Words that come from the heart, enter the heart."
It therefore follows that if you seek to have a positive influence on your fellow and are unsuccessful, the fault lies not with that person, but with yourself. Had you truly been sincere, your words would certainly had an effect.
Outreach influence To what extent is that true? Didn't Moses and the Prophets speak from their hearts to the people yet their words did not enter the hearts of the majority?
More clarity please!
Of course, the Prophets spoke from the depths of their beings but when it comes to moral choices one's freedom of choice is never averted. One may choose to heed the words of the prophet as the divine injunction is, or not to obey. The above teaching, however, is more about teacher-student relationships where an inspiring teacher will find a pathway to the student's heart.
See also this link for some more insight on this specific teaching.