Pillar was demoted after video showed him tossing his bat in disgust after being pulled in a game against the Yankees. At the time, Toronto manager John Gibbons explained the move by saying "there was no room for selfish play."
Pillar, 25, said he had talked to Gibbons about the incident and was relieved that it was considered "water under the bridge."
"Leaving under those circumstances weighed pretty heavy on me when I first went down there (to Buffalo)," the player said.
Pillar said he will continue to play with emotion but added "It's just about controlling the emotions and understanding that at this level the camera's always on you.
"You can't have a moment of weakness, a lapse of judgment like I did. It's definitely a lesson learned and I went down there (to Buffalo) and just became a better person for it. And really wanted to prove to this organization that what happened was a one-time thing and it won't happen again and I learned from it."
The Jays wasted little time using Pillar. With Colby Rasmus said to be under the weather, Pillar started Tuesday night in centre field against the visiting Boston Red Sox.
Pillar said he took his medicine in the minors.
"I went down there and I did what I thought I was capable of doing — went out there and played hard," he said prior to Tuesday's game. "I was a good teammate, tried to be a leader in the clubhouse and help that team make the playoffs."
Pillar also racked up some impressive numbers. In 100 games for Buffalo, he hit .323 with 39 doubles, three triples, 10 homers and 59 RBIs. That earned him selection as an International League all-star.
It also won him a third stint with Toronto this season.
"Pillar's been playing so good down there," Gibbons said. "We still think we've got a pretty good player there."
The Jays sent outfielder Nolan Reimold to triple-A Buffalo to make room for Pillar.
"Reimold's been struggling a little bit. And he wasn't getting a whole lot of playing time," said Gibbons. "It just kind of all came together."
The 31-year-old Reimold hit .212 in 22 games for the Jays.
Prior to Tuesday night's game, Pillar was hitting .225 in 26 games for the Jays this season