Gregory said any issues in his past were the result of immaturity and stubbornness, not drug use.
"That's something I've definitely been working on and something I can definitely fix," Gregory told ESPN Radio last Friday (via The Dallas Morning News). "I'm 22 years old but I think I carry myself real well and I think I need to carry myself a little bit better as far as decision-making goes.
"I think a lot of people are getting tied up in the weed and think it's just a weed problem. I don't think it's a weed problem. I think it's decision making. I think I'm immature. I'm definitely working on that. I want to prove everyone wrong and I want to do it with this team. I think this is the best team I can do that with."
Gregory said he has successfully stayed away from marijuana.
"I haven't touched it," he said. "I'm feeling real good, too. This is a high in itself, to be honest. I'm high on life right now, and I don't want to lose this high."