CM Punk says he's got a "gift" for his fans when he walks into the Octagon on Saturday -- telling TMZ Sports ... "I'm sharp and I'm ready and I'm focused."

Punk will make his long awaited return to the Octagon at UFC 225 against Mike "The Truth" Jackson ... it's CM's first fight since he lost his UFC debut against Mickey Gall in Sept. 2016.

"I lost pretty spectacularly in my last fight but I learned so much," Punk tells TMZ Sports.

One of those lessons ... Punk says he needs to control his emotions and take his time when the bell rings -- "not try to hurry up and just enjoy being in there."

UFC champ Tyron Woodley previously told us Punk has been busting his ass like a maniac in the gym ever since his first fight ... sometimes working out 3 or 4 times a day.

Punk says he's "hyper-focused" on getting a win ... but that's not the only measure of success. The most important thing is to grow and get better as a fighter.

And if he wins ... Punk says he'd be down for a rematch with Gall -- but don't get it twisted, he's laser-focused on Jackson.

There's more ... Punk also says he's had a "real hard emotional couple of weeks" -- a reference to the WWE doctor who sued him over negative comments Punk made back in 2014.