"Today was a lot about my winners and my errors," Williams said. "I made some spectacular winners and some spectacular errors, but in my head I just wanted to keep playing aggressive because that's my game and I know that as long as I keep doing that they'll start landing.
"It's not easy, but then if I stop being aggressive and start playing her game, that's when I'm really in trouble.
"I was just missing shots and eventually they are going to start going in. There are only so many you are going to miss. My mindset was that it was going to land."
It means the dream final between Williams and Ana Ivanovic is still possible. Ivanovic was ruthless in dispatching Sweden's Johanna Larsson 6-1, 6-1 in just 43 minutes.
The Serb will now play Japan's Kurumi Nara, who has dropped only two games in the tournament so far and yesterday beat compatriot Ayumi Morita 6-0, 6-1.
Williams will face rising Spaniard Garbine Muguruza, who is playing her first tournament since Wimbledon (ankle surgery ruined the second half of the year). Williams has faced Muguruza once before, winning 7-5 in a deciding third set in Brazil, but Muguruza showed last year she is one to watch after making the fourth round at both Indian Wells and Miami.
Williams is on her latest comeback after a back injury restricted her to just 11 tournaments last year and the world No 49 is equally keen to climb the rankings. She has high expectations.
"I never set limits on myself, or anyone for that matter," she said. "I think the most surprising thing I have learned in life is you can accomplish a lot more than what you think you can if you allow yourself to do it and aren't afraid and don't hold back. With effort, you achieve so much."
Ivanovic barely broke into a sweat against Larsson - she broke the Swede five times and faced only one break point on her own serve - as she illustrated why she is the world's No 16.
"I was really happy with today's performance," she said.
"I really didn't do too much wrong out there.
"I felt good on court and my timing and rhythm were good. I didn't think about the score, stayed in the moment and did really well."
Both Williams and Ivanovic are clearly the crowd favourites in Auckland and Williams admitted she doesn't always get that wherever she plays.
"Here I feel like a Kiwi. I feel so good out there. When I win a point they are like, 'yes', and when I lose they're like, 'ohh'. You don't get that everywhere. The places I do, I feel so grateful. I love it."
ASB Classic - Day 4
Centre court 12pm
Q - Sachie Ishizu (JPN) v 3- Kirsten Flipkens (BEL)
Kurumi Nara (JPN) v 2-Ana Ivanovic (SRB)
Lauren Davis (USA) v 5-Jamie Hampton (USA)
Not before 6.30pm
Garbine Muguruza (ESP) v Venus Williams (USA)
Sharon Fichman (CAN)/Maria Sanchez (USA) v 4-Mona Barthel (GER)/Megan Moulton-Levy (USA)
Court 4
WC-Kirsten Flipkens (BEL)/Ana Ivanovic (SRB) v 3-Lucie Hradecka (CZE)/Michaella Krajicek (NED)
