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Johnson triumphed last year with a birdie on the second hole of a sudden-death playoff to edge out fellow American Troy Matteson, and he has posted sub-70 scores in his last 16 competitive rounds on the par-71 layout.
"Fortunately I have had some success here, but I am trying to put 2012 behind me," the 37-year-old told reporters on Wednesday.
"It's not like just because I won, I've got a three-shot lead going into Thursday so I frankly have to put it behind me, and that's going to be my approach.
"I love the golf course. It's in great shape, as usual, and I just like coming back and seeing faces and friends and family that I love. It feels like my backyard in a lot of respects."
Johnson has not triumphed on the PGA Tour since he clinched his ninth career title at the TPC Deere Run 12 months ago, but was delighted to be producing much improved form since making an erratic start to this season.
"My golf game was not where it needed to be early on in the year," said the Iowa native, who missed the cut three times in his first seven events. "That was just a process to kind of get where I am now.
"I was off fundamentally more than I care to admit, especially with my driver, and if I can't drive the ball in the fairway, then it's going to be difficult for me. And now my driver is probably one of the best clubs in my bag again.
"I like the direction it's going," Johnson said of his overall game. "I've just got to be patient. My putting has been very up and down so any given week you've got to putt well to climb the board and hopefully this is one those weeks."
Johnson faces a strong field in the final PGA Tour event before the year's third major, the British Open, gets underway at Muirfield in Scotland in nine days' time.
Also competing this week are former major champions Louis Oosthuizen, Keegan Bradley, Lucas Glover and Yang Yong-eun, and American world number 11 Steve Stricker, who won the John Deere Classic for three years in a row from 2009.
