Albert Schweitzer (January 14, 1875 – September 04, 1965)
To educate yourself for the feeling of gratitude means to take nothing for granted, but to always seek out and value the kind that will stand behind the action. Nothing that is done for you is a matter of course. Everything originates in a will for the good, which is directed at you. Train yourself never to put off the word or action for the expression of gratitude.
Not one of us knows what effect his life produces, and what he gives to others; that is hidden from us and must remain so, though we are often allowed to see some little fraction of it, so that we may not lose courage.