Happy Days star Henry Winkler suffered from undiagnosed dyslexia until 1981, and the struggles it caused made table reads “humiliating.”

The former Fonz has spoken out about his disorder many times over the past four decades. In an excerpt from his upcoming memoir, Being Henry: The Fonz…and Beyond, he explained how dealing with dyslexia affected his career and self-esteem and how angry he was when he learned he had a condition that was entirely out of his control.

“Even in the midst of Happy Days, at the height of my fame and success, I felt embarrassed, and inadequate. Every Monday at 10 o’clock, we would have a table reading of that week’s script,” Henry Winkler wrote, per PEOPLE. “And at every reading, I would lose my place, or stumble. I would leave a word out, a line out. I was constantly failing to give the right cue line, which would then screw up the joke for the person doing the scene with me. Or I would be staring at a word, like ‘invincible,’ and have no idea on earth how to pronounce it or even sound it out.”

The now 77-year-old explained that he couldn’t get his mind and eyes to work in tandem, and he felt like he was putting extra stress on the cast and crew of his classic TV show because he had trouble making sense of his scripts. The condition makes it difficult for the brain to connect sounds and letters and often makes the eyes see letters out of order. Dyslexia is fairly common and affects around 20% of the population. With proper intervention, it is treatable. 

“My brain and I were in different zip codes. Meanwhile, the other actors would be waiting, staring at me: it was humiliating and shameful. Everybody in the cast was warm and supportive, but I constantly felt I was letting them down.”

Henry Winkler Was Furious When He Learned About His Disorder

To deal with the complications, Winkler requested his scripts early, so he could study them prior to readings. He felt like that was an unreasonable request because the writers were already “under the gun.”

Henry Winkler had himself tested after his stepson was diagnosed with the same condition. When he found out he had dyslexia, he wasn’t relieved. He was furious. 

“[When I] found out that I had something with a name, I was so f**king angry.”

“All the misery I’d gone through had been for nothing,” he continued. “All the yelling, all the humiliation, all the screaming arguments in my house as I was growing up — for nothing…. It was genetic! It wasn’t a way I decided to be! And then I went from feeling this massive anger to fighting through it.”

Henry Winkler now devotes himself to dyslexia awareness. Aside from publicly speaking about the condition, he also authored several children’s books starring a character who struggles with the disorder.