SAN FRANCISCO—Lexi Thompson needed to get her mind right before she could get her golf game back and now is in position to win her second career major. Thompson shot a bogey-free 5-under 66 on Saturday to take the lead into the final round of the U.S. Women’s Open for the first time in her career with a one-shot edge over teenager Yuka Saso. “I haven’t played to my standards and what I need and I just realized that I needed to change my mindset,” Thompson said. “It was only hurting me. Obviously, I needed to work on some technical things in my game and everything, but the mental side was really getting to me. I was just taking it way too seriously and thinking that Lexi depended on my score.” Thompson said she’s been working again with performance coach John Denney about not dwelling on mistakes although she made …