The 42-year-old, who emerged victorious in Augusta in 2004, 2006 and 2010, is chasing his fourth title after a triple-bogey seven at the short fourth dropped him to a tie for third last year.
"I think what makes the Masters so exciting is having an opportunity to win; playing the back nine with an opportunity," Mickelson told BBC Sport.
"That is what is so enjoyable, exciting as a player. And I've been fortunate to come out on top a few years and I've been unfortunate to have a number of them come close but not quite good enough.
"But either way, having that opportunity to be in the thick of it and to feel that excitement, to feel that pressure, to grace Amen Corner knowing that you need birdies and trying to win a green jacket, that is the greatest thrill a golfer can possibly experience."
Mickelson recently took the last week before the Masters off for the first time in years.