Day slipped from 10th to 37th in the world ranking during 2012 due mainly to off courses distractions including the arrival of he and wife Ellie's first child Dash.
Day recorded just three top tens in 17 starts in 2012 compared to ten in 21 starts in 2011 including runner-up finishes on debut at the Masters and the US Open.
Tomorrow Day will face Matt Kuchar in one of the semi finals with the winner to face the victor between Ian Poulter and Hunter Mahan.
Day comfortably got past Bubba Watson in today's round of 16 and in this afternoon's quarter final defeated Graeme McDowell in a very closely fought match with the Australian winning 1 up after trailing 2 down through three holes.
Day was never behind in his morning match against Watson eventually winning at the 15th by a 4&3 margin.
After his win against McDowell Day summarised the day's efforts. "It was very stressful out there today. I feel like my mind is going every which way right now. Just to play the way I did on the back nine was very, very special. The whole game today felt really, really nice, and I'm looking forward to tomorrow. You know, myself and G Mac, we really didn't play our best, but you've just got to do enough.
"That's because you're just playing against a guy that's across the tee from you. I've got Matt Kuchar tomorrow, and I know he's very slow and steady, hits a lot of fairways and greens and can roll the rock when he can, and I'm looking forward to that.
"Last year I felt like I found excuses rather than put the blame on myself. I just didn't work hard enough. And this year is totally different. I've got a lot of the stuff behind me. Dash was born last year and a lot of injuries happened last year, but that was in the past now.
"I just wanted to get off to a great start this year, and I worked very, very hard in the off season, in the gym, and I worked really hard with Cole right before we started the TOUR, and it seems like it's working out great.
"I just started working with some guys, Jason and Henry. They're from a little company called Focus Band, and that's why my mental game has been a lot better this year. I just started working with them at the Waste Management and finished sixth at Pebble, and I'm in the final four this week. All the things, the little things that I've been working hard on are starting to pay off, which is nice. Hopefully I can keep improving each week and maybe win some."
Day's semi final opponent Matt Kuchar defeated Robert Garrigus in the quarter final after victory over Nicolas Colsaerts and the face-of between he and Day promises to be a great battle to reach the final.