Think of someone who has influenced you and taught you how to act. Even if you have lost touch with that person, what they have taught you will never be forgotten.
It's comparing how a piece of clay is like molding a life. You can affect how they are when they are still fresh and leave a mark. After a few days or years, the person grows and develops into their own personality. They do not change as easily now but the lesson you taught them will stay with them forever.