Bryant was involved in sideline confrontations with both quarterback Tony Romo and safety Jason Witten during Sunday's 31-30 defeat to the Detroit Lions, although he stressed that he has no issue with either teammate.
Garrett accepted that the altercations were fuelled by Bryant's desire to see his side win, but urged the 24-year-old to use that passion in a positive way.
"Dez is as well-liked a guy on our football team by his teammates and by the coaching staff," Garrett told reporters. "He's very passionate about the game, he loves football, he loves his football team and he wants to win.
"One of the things he has to learn is to channel all that positive stuff, all that positive emotion, he has to channel it and focus it to the task at hand. That's something we talk to everybody on our football team about. It's really important you're able to do that. Go to the next play, get yourself ready for the next situation, and Dez has done that a lot.
"He has matured a lot in the last three, four years since he's been with our football team, and that's an area where he has to get better. It's something we addressed with him during the game, something we addressed with him after the game, but you never want to take away that passion, that spirit that he has."
Garrett further praised Bryant for his professionalism.
"Dez is the farthest thing from [a prima donna]," he added. "Dez is a great teammate. He loves this team. He's very passionate about football.
"He's a great competitor. He loves to work at it. He loves to practice. He loves to play. He wants to win as much as anybody I've ever been around. His teammates love him. His coaches love him.
"Again, the only issue there is we've got to channel all that enthusiasm and channel all that emotion in a positive direction. He understands that. It's part of maturing."
Bryant scored two touchdowns in Sunday's match but found himself on the losing side after Lions quarterback Matthew Stafford went over with just 12 seconds remaining.