After turning down Barca over the summer, Williams was barracked by home fans during Athletic's defeat at Montjuic earlier this season.
Williams recalled to El Mundo: "I was surprised, I won't lie to you. But well, I didn't give it much importance because when you go to the rival pitch it's normal for them to boo you, what happened is that this time it was a personal matter.
"It's fine, I think it's even funny as long as they're not insults. Being booed is the essence of football and I handle it quite well.
"In the end, you have to live with it. Football works like this, with so many interests from clubs, the media, the players... and there is always noise. It is neither bad nor good, it is what it is and it does not affect my performance. I continue to do the same job I have done until now.
"Personally, there have also been tough moments in which you stop to think about so many scenarios and it is difficult, but I have an incredible family and friends who support me. I want to think that this will not happen to me every summer."
On Athletic fans, he added: "The fans are very happy that I'm staying here and I'm very happy to be here. Bilbao is my home, I want to continue enjoying it and the truth is that I'm very happy. I've always had things very clear and I think people see that.
"I think I'm doing really well and I'm trying to bring Athletic to the best of Spain and Europe, with that final in San Mamés that excites us so much. That's the only thing that matters now."