Maybe be their opinion doesn't matter at all, but sometimes, it is enough for us to keep going.
One may forget the exact words, but one cannot possibly forget how some person made him feel about himself. May be that feeling has to remain with us all the time, as a constant reminder to push ourselves & to bring out the best in us.
Eventually someone's such highly opinionated words turn out to be the biggest motivator in our life.We have to keep fighting, trust our guts, and stay faithful to our efforts. And some fine day, our efforts will prove that someone wrong!