Jackson, promoted from Triple-A Iowa on Aug. 5, entered Wednesday's game with 16 strikeouts in 28 at-bats. He totaled 158 K's in 100-plus games this season in the Minor Leagues.
In Jackson's first at-bat of Wednesday's 7-2 win over the Astros, he laced an RBI triple to knock in his first big league run. He finished 2-for-4 with a run on the afternoon.
"Every day, [hitting coach James Rowson] is challenging me," Jackson said before the game. "It doesn't change overnight. You've got some things built into your muscle memory that are hard to break. It may take a while, but I'm working every day to knock that out. I have the talent, I have the ability to be a really good hitter in this league."
Jackson, who was the Cubs' first-round pick in the 2009 First-Year Player Draft, is trying to simplify his swing, shorten his bat path and slow down some of the moving parts.
"I've always gotten away with movement, because I have really fast hands, so I could move and still catch up to balls, but it also leads to a lot of swings and misses and foul balls and a lot of strikeouts," Jackson said. "We know that's my favorite area of the game to talk about."
Jackson, 24, batted .256 at Iowa, and he admits he may have been pressing.
"Being in Triple-A and knowing how close I was caused me at times to press a little bit," he said. "Being here and having coaches who I know are behind me, working with me every day, I think it's a really good environment, positive environment so I can become the player I want to become."
It's not for lack of effort. Jackson is in the cage with Rowson every day.
"I know I can compete," he said. "Someday, hopefully sooner than later, these things we're working on will start really taking effect in the game. I think you're looking at a player who will be a big force in the lineup."