The Mavericks fell to a 129-114 defeat to the Lakers at the American Airlines Travel Center on Friday.
Doncic had a double-double with 25 points and 10 rebounds to go with seven assists, though he did turn the ball over six times.
However, his anger at what he believed to be a sub-par performance boiled over in the second quarter when he was unable to convert from the line.
"I played very bad. I felt like I don't know how to play basketball. I've got to get better - a lot," Doncic said afterwards.
"I'm competitive, and like I say, I've got to get better at a lot of points. A lot better.
"I know I can get better. There's a lot of things. I'm 20 years old. I've got a lot of things that I can do better, I can learn better. So I'll get better."
Luka Doncic is not a fan of Dallas’ new jersey pic.twitter.com/YJ4LvE9uzD— Jon Machota (@jonmachota) January 11, 2020
Coach Rick Carlisle, who was ejected from the game for berating the officials for allowing a Lakers timeout from an out-of-bounds play, after the Mavericks had already inbounded the ball, had plenty of sympathy for Doncic.
"He is a guy that wants to win, and he gets frustrated," Carlisle said. "Those are emotions and feelings that are about winning and losing, and so I get it. I get it.
"He's going through a lot this year. He's going through just a lot of different situations - some phenomenal performances and other nights where people are just taking physical liberties on him and beating the s*** out of him.
"He's learning how to deal with all that stuff, but it's not easy.
"You know, when I was 20 years old, I was walking around as a freshman at the University of Maine. I didn't know whether to s*** or wind my wristwatch. And this guy is a second-year player, and he's going to be a starter in the All-Star Game.
"I think we've got to understand that he's still young. He's mature beyond his years in terms of how he sees the game and his skill set and how he can do things out on the floor, but we're going through a rough stretch right now. Everybody needs to try to keep their emotions in check."