"Sometimes you are rolling off three or four hours' sleep. Before I was pretty intent, pretty strict on how I would try and sleep, pretty uptight about all those little things but now I don't mind it all.
"Sometimes I love it when you hear a funny noise in the middle of the night and you jump up and make sure they are still breathing. Life is a beautiful thing and I've definitely been blessed to have a child and I just want to be the best father I can."
He said one of the most pleasing things was that she looked like his mother and not him.
"It's funny when people say you don't know the feeling until you have one - you really don't. The first time I [saw] her, you see a little nose on her, big ears on her, little feet - it's just a beautiful thing.
"It's been crazy. I'm missing them so much.
"We've been lucky the Chiefs have set me up a house and the things that my wife and little one need ... I actually really love Hamilton, eh. It's a really chilled-out environment and obviously being a new father it's an awesome place for me and my wife to start a new life with a little one. Get a bit of free time, down time with her."
Williams said having a child had made him even more determined to do well in boxing and rugby so that he could provide for his family, and he believed gearing up for his fight with Chauncy Welliver at the end of the month was the best way to prepare for his season with the Chiefs.
Sonny Bill Williams and his wife Alana Raffie.
"It refreshes me mentally, gets me away from everything else - rugby or rugby league. It puts me in a place when I'm just thinking about the fight, and once that's over I feel physically in the best shape possible and mentally I'm feeling pretty good as well."
While both Williams and Chiefs coach Dave Rennie admitted there was some concern about him getting injured before the season, they also said it was no different from any other sport and a risk they had to take.
Rennie said what he had seen so far of Williams' form was "phenomenal" and he was pleased to have him back.
"He's in good nick and it was a really good signal him coming in and being in that sort of condition."