Johnson (19-5) dropped Cormier in the opening 30 seconds with an overhand right, but ultimately tapped to a rear-naked choke in the third round. It was his first loss in three years and his first setback in the 205-pound division.
"Hell no, I'm not happy with that fight," Johnson told ESPN.com. "If it would have been my way, I would have stayed patient and picked my shots like I usually do. But I had it in my mind, I was so set on finishing the fight in the first round. It messed me up.
"The whole time after the fight, I was thinking about the mistakes I made that helped Daniel win. If I hadn't smothered my punches when I charged him, things would have been different. You always think about what you could have done at that moment to change the results, but DC is a champion and when you're a champion, you know how to make adjustments. He did and he pulled it off."
Johnson, 31, returns to the Octagon this weekend at UFC 191 in Las Vegas. He'll fight another talented standup fighter in Jimi Manuwa (15-1), whose résumé boasts 13 career wins by knockout.
Originally, the UFC scheduled Johnson to fight Jan Blachowicz (18-4), who is actually coming off a loss to Manuwa in April. Johnson admits he wasn't very excited about that matchup and was happy to see the change in opponent.
"For whatever reason, I wasn't as motivated when I was supposed to fight Jan," Johnson said. "I was motivated, but not as motivated. I just saw him lose against Manuwa. I was like, why would they put me up against this guy?
"I wanted someone that was actually going to be competition, somebody who would get me excited. When they gave me Jimi, that definitely lit a fire under my ass. I said, 'Cool, let's do this.'"
While it might not show against a fellow striker in Manuwa, Johnson has spent the last four months working extensively on his ground game. He has a new full-time grappling coach in Neil Melanson, a former coach at Xtreme Couture and Alliance MMA.
Johnson says he has recognized a hole in that area of his game -- four of his five career losses have come via submission -- and his new partnership with Melanson should help. In addition to being a wealth of knowledge, Melanson is a big body for Johnson to roll with on a regular basis.
"I'm still working on my ground game," Johnson said. "I've trained the rear-naked choke I tapped to a million times, but some reason, I always panic when I get into that position in a fight. I don't know why. I've made some adjustments and I've got Neil Melanson helping me out.
"It wasn't a cardio issue, that's for sure. I was tired as hell but I just panicked on that choke."
Unfortunately, the focus on Johnson heading into UFC 191 has detoured from his actual fight over the last month, as the promotion was forced to investigate a matter involving Johnson and a female patron at his gym in Boca Raton, Florida.
In a Facebook post on Aug. 18, Johnson ranted about an incident with an unnamed woman, whom he called "ugly." The message was apparently directed toward the female and Johnson promised to "snatch the [yoga] mat" from under her if she got in his way.
Johnson, who has been accused of domestic violence in the past, has since apologized to the woman and agreed to undergo counseling. He has also agreed to make a donation to a women's charity, but has no further details at this time.
"Everything that happened, happened -- and there's really no point in sugarcoating it," Johnson said. "I apologized to the girl and moved on. It is what it is. She accepted my apology and now we're cool.
"I knew I was wrong saying the things I said, and I'm man enough to admit when I'm wrong. I apologized and life goes on. I never said I was perfect. I'm human. I'm talking to the UFC about [the details of the donation] now. We're discussing what I need to do."