How can one say that he/she has made a difference?:
When your time on earth is over, to the extent that people remember you fondly, and are changed for having known you, you have made a difference.  I rest all of my hopes on the upbringing of my children.  If I am a good father, and I believe I am, my children will be positively affected throughout their lives by the values I have taught and the examples I have provided.  I also try to do so through various mentorship programs for those whose reality would be darker but for my involvement.  I am satisfied that my involvement in all of these people's lives will have made a difference, and that they are better off having known me than they would have been otherwise.