Costa's quality was never in doubt after he fired Chelsea to the Premier League title two years ago, but the Spaniard found himself in hot water time and again due to his volatile temperament.
The 28-year-old cut a miserable figure last season as he squabbled with opponents and even rowed with Chelsea team-mate Oscar on the training ground.
But Conte has managed to tame the worst of Costa's excesses since taking charge at Stamford Bridge during the close-season and the forward is now able to channel his energy into goalscoring instead.
The results have been spectacular and Costa maintained his resurgence with his 12th league goal in 15 appearances this season to seal the leaders' 1-0 win over West Bromwich Albion on Sunday.
"I'm happy for him because he is showing great passion. In every game he is showing great commitment and work rate to help the team," Conte said.
"It's fantastic and it's important to continue this way. Diego for sure is a great striker.
"He is enjoying playing his football. Now he is showing his passion in the right way.
"If you ask me why he didn't in the past I don't know. I can talk very well about his commitment and his behaviour in the training sessions."
With no bookings in his last 10 matches, Costa has so far managed to avoid the yellow card that would trigger a suspension for his fifth booking of the season.
Conte would love his star striker to continue to toe the line until January to ensure he is available for all of the busy Christmas period.
"It's incredible because after the Arsenal defeat Diego had four yellow cards. He was on the edge but he continued to stay on the edge and not go over. I think he can arrive at January without a yellow card. I hope!" Conte said.
"I always tell my players to stay focused on the football. I don't like the provocation. I'm trying to transfer this. I'm very lucky because my players know this."
Chelsea's ninth successive league win reopened a three point lead over second placed Arsenal, but Conte refused to get carried away when asked about Chelsea's chances of winning the title in his first season in England.
"Now it's important to think of the next game at Sunderland because we have only two days to prepare this game," he said.
"It's important to be focused because this is an important period. We have a lot of games in the Christmas period. It's important to win and play with a good intensity."
Chelsea have a relatively unthreatening list of fixtures in the coming weeks, raising the possibility of equalling Arsenal?s Premier League record of 13 consecutive wins in one season.
"I'm interested in continuing this way, but I'm not interested in the record," Conte said.
"I'm interested in three points because it means we will stay top of the table and fight for something important."
Albion were unlucky not to take what would have been an impressive point after stifling Chelsea for long periods and boss Tony Pulis was impressed with the way his team matched the leaders.
"They play a different formation than most teams in the Premier League, but we had a good week working on it and I thought we were well set up," Pulis said.
"The goal is disappointing because Gareth should have dealt with it, but I've no qualms with anyone because they all played well. "
They put so much effort into the game and it took a wonderful goal by Costa to beat us."