My schooldays were not happy days for me. I was bad at mathematics, science, English, spelling and reading, and was criticised by almost everybody. I loved drama but I was not allowed to be in school plays because my grades were too low.
My schoolwork wasn't helped by the fact that I suffered from dyslexia. I wasn't diagnosed until I was in my thirties, when, by chance, my stepson was found to be dyslexic and I realised I had the same thing. My struggles at school caused friction with my parents, Jewish immigrants who fled Nazi Germany in 1939 and set great store by education.
But in this sea of negativity was one teacher who, in 1961, when I was 16 years old, said a single sentence that changed my life. Donald Rock was my music teacher at McBurney School, a private boys' school in New York City. Mr Rock was in his fifties then, a natty dresser with short grey hair and a cleft lip that he covered with a moustache. He was strict but less so than other teachers.
Mr Rock was the one who gave me hope. He took me aside one day and said: "You know, you're going to be OK, you're going to be all right." It was the first time anybody had ever said anything like that to me. Everybody else had told me that I would never achieve anything.
That single sentence has inspired me and stayed with me all my life. It helped me to overcome my parents' objections to my ambition to become an actor. They wanted me to take over the family import-export business, but I was determined to follow my gut feeling.
It helped me to make it to Emerson College in Boston and then Yale School of Drama in Connecticut. I went on to work in television series and advertisements, but my big break came when I was cast as Arthur Fonzarelli, nicknamed "The Fonz" or "Fonzie", in Happy Days, in 1974. The Fonz was everything I wasn't, everything I wanted to be. But it was a great part and I was lucky enough to play it for 10 years.
It's the role I'm best known for, even though I have appeared in, produced and directed many TV series and movies and have been lucky enough to win a string of awards. It all started with Mr Rock's words and I have made it my job to repeat his sentence to every child I meet. With encouragement and self-belief, children will find their passion and be happy. I started with my own children. Like me, they are all dyslexic and I told them that they would be OK. They're doing fine.
I have also written many children's books in collaboration with Lin Oliver, including the Hank Zipzer and Ghost Buddy series. I have been touring the US and the UK since 2008, reading to children from the Zipzer books, about a boy who is dyslexic and the "world's greatest underachiever". I want to get the message across that if I can make it, anybody can.
At the schools, I see lots of little Henry Winklers. When I arrive they look bored, but when I tell them that I am in the bottom 3 per cent academically in America yet I've written a series of books with my partner, it helps them to see that anything is possible.
I don't know why Mr Rock chose to make that remark to me all those years ago. But he planted a seed that grows within me to this day. It's only in retrospect that I can understand how powerful a simple sentence can be.
Henry Winkler is appearing in the new series of Arrested Development and is writing the latest book in the Ghost Buddy series. Last month, he received an award from the United Federation of Teachers in the US for his work with schoolchildren who have special needs. He was speaking to David Harrison.
Born: 30 October 1945, New York City, US
Education: PS 87 William T. Sherman School, New York City; McBurney School, New York City; Emerson College, Boston; Yale School of Drama, Connecticut
Career: Director, producer and author. Starred in Happy Days between 1974 and 1984.