The Argentina captain suffered a number of injuries last season as Barca failed to win a major trophy, before his World Cup dream was ended by Mario Gotze's extra-time winner in the final.
But Messi has bounced back to break La Liga's goalscoring record and move to 300 league appearances for Barca this term.
And the man named the world's best player on four occasions told Mundo Leo: "The truth is that this year I tried to get to my best form as quickly as possible.
"I knew I was coming off the back of a not very good year, during which I went through a lot of problems on and off the field.
"It was a challenge to change the image that I had given out last season and to be the player I had been in previous seasons again.
"That was my objective and that's how I came out at the start of this season, really up for it."
Under Luis Enrique, Barca are on an 11-match winning streak and remain in the running for La Liga, UEFA Champions League and Copa del Rey success.
And Messi feels things are looking positive for the Catalan giants.
"The truth is that we're in good shape at the moment," he added.
"Luckily, after the match against Real Sociedad [a 1-0 loss on January 4], where we didn't start the year very well, everything changed.
"Now there is a different dynamic to the team, everything we do comes off. The team has a lot of confidence and we're changed the attitude and drive.
"That's why we're playing like we are at the moment, but there is still a long way to go."
