In combat sports, there is always a fine line between winning and losing.

The simplest of mistakes can result in a loss, not to mention bodily harm. Every athlete is human, and thus capable of making a mistake. That goes for their coaches as well.

ESPN asked several of the best trainers in mixed martial arts to reflect on a mistake they've made. Most struggled to identify just one as the biggest of their career, but were able to come up with a specific example.

Fighting is undeniably an individual sport, but there is a team element to it nevertheless -- which you should get a sense of reading these.

Jason Parillo, RVCA VA Sport

Coaches have egos just like fighters. I've let ego get the better of myself and supported fights, even when I knew we were in over our head. I could have gone against the grain, but I still supported it.

Honestly, the best example is when BJ Penn [moved up in weight and] fought Georges St-Pierre the second time [UFC 94, January 2009]. Not because I didn't have confidence in BJ -- especially at that time. He was killing people. BJ was really unstoppable back then, but I understood the game of fighting and I understood weight classes.

Both guys were UFC champions and the amount of money being generated from that fight, I just didn't feel I was in a position to go against it. I'm not a manager. I'm a coach. It's not really my job to say, 'Take that fight, don't take that fight.'

But looking back, I would have definitely been against it. Again, not because I didn't think Penn could beat 'GSP,' but it sent him in that direction of fighting at 170 pounds, when he was on his way to being recognized as the best 155-pound fighter of all time.

In my opinion, there is a lot of ignorance in this sport. Anybody can break in. A businessman can come in out of the woods and be a manager. A lot of these guys have egos and they're controlling these kids' careers. They should take it upon themselves to do what's best and talk to a fighter's coach, before they even get feedback from the fighter, on what direction they're going. That's something I've seen in boxing that this sport could learn from.

Mark Henry, New Jersey striking coach

I believe I overtrained Frankie Edgar for the second Jose Aldo title fight [UFC 200, July 2016]. He was looking very explosive for about the first month of camp -- quick twitch, reacting fast -- and then the last four weeks, it just fizzled out. We totally overtrained him.

It was like watching two different people, which I had never seen. I just wanted it so bad for him. His second UFC title, and the first fight with Aldo was so close. The 'want' took over a little bit. Not that it was the reason we lost, but that was one of his worst fights. He looked slow. His shot was off.

The last month of camp, I was telling [UFC bantamweight] Marlon Moraes, 'We've got to slow him down.' And I tried to slow him down closer to the fight, but I'd never said that to him before and he kind of took it as an insult. My problem was I waited until the very end. Psychologically, that wasn't good. You don't want to do something you've never done before that close to a fight.

Everybody is different. Everybody has different injuries, they're getting older, the bigger guys can't work as hard as the smaller guys -- it's all different. We used to have a base plan: This is the way we do it because you figure that formula works. You definitely can't do it that way.

American Kickboxing Academy coach Javier Mendez admits to having "two big, big screw-ups with Cain Velasquez." Josh Hedges/Zuffa LLC via Getty Images

Javier Mendez, American Kickboxing Academy

I've had two big, big screw-ups with Cain Velasquez. The first was when he lost to Junior dos Santos [UFC on Fox, November 2011] with a knee injury. My gut instinct was I didn't want him to fight and it shouldn't have mattered how important the fight was. I should have pushed for that and I could have pushed for that. I was saying things like, 'I wish you didn't have to fight,' instead of, 'You shouldn't fight.'

And the other bad one was the altitude in Mexico, before the Fabricio Werdum fight [UFC 188, June 2015]. I tried to get him down there early to acclimate and he wouldn't do it. He said, 'I'll go 10 days before,' and I just gave up and said, 'OK, with your cardio that should be fine.' I should have insisted we go earlier. That was my fault. We got down there and his very first workout with Luke Rockhold, I knew we were in trouble with the altitude. I was crossing my fingers hoping we'd be OK, but 30 seconds into the fight I knew we were in trouble.

Trevor Wittman, Grudge Training Center

There's been so many mistakes, so many learning lessons. One that stands out because it was somewhat recent was Rose Namajunas's title fight versus Carla Esparza [TUF Finale, December 2014]. We went into a fight where I felt like -- I just completely brought her to that loss.

I didn't say anything about it being a five-round fight. Here's Rose with this lack of experience, I think she had something like three pro fights at the time, coming off The Ultimate Fighter reality series where she had different coaches and the fights were only two rounds. I didn't talk to her at all about the five rounds.

I was almost like a fan or hers after the show. She's such a great finisher and was throwing all these amazing kicks. Against Esparza, she threw 15 kicks in the first round and maybe another 17 in the second. That is so fatiguing. But it was like I was a cheerleader in the corner instead of a coach and I was so upset with myself in that fight, that I came in underestimating Carla Esparza's fundamental wrestling. I felt like I led Rose into that fight, knowing she lacked experience, but that being offset by, 'Oh my God, she's such an amazing fighter.' I 100 percent take responsibility for it.

Mike Brown, American Top Team

I don't know if this is my biggest mistake, but it's definitely one I remember and that I learned from.

I cornered Yves Edwards against Isaac Vallie-Flagg [UFC 156, February 2013]. I was kind of new to coaching. I was actually still fighting at the time. Two rounds went by and they were close, but I thought we'd won them. I told Yves, 'Hey, you're up 2-0. Don't do anything stupid. Be careful.' He ended up losing the third round and lost the fight by split decision.

I didn't factor in, 'Oh, in a close round, it might go to the other guy.' When it's close, you have to assume you lost. Even if you're pretty sure you won, you have to assume you lost. Now, I'll tell my guys, 'We've got to go out and win this next one.' I might really believe we're up 2-0, but maybe it was close enough a judge can screw it up.

Anthony Pettis's weight cut for his fight with Max Holloway "was pretty scary" according to his coach Duke Roufus. Jeff Bottari/Zuffa LLC/Getty Images

Duke Roufus, Roufusport MMA

The biggest mistake I've ever made is being a part of [UFC lightweight] Anthony Pettis fighting at 145 pounds. What all fighters can learn from that is get better at your own weight class. Losing weight is not the answer.

It was bad in Toronto [when Pettis missed weight for an interim title fight against Max Holloway last December]. I'm the one who pulled the plug on his weight cut. He was having some bad seizures almost, it was pretty scary. I'm behind what California is doing with weight cutting. I've never agreed with the weight cutting culture in this sport. I hope the UFC does add more weight classes. It won't dilute the weight classes, it will be more champions for them to promote.

John Crouch, MMA LAB

I would have to say a couple of personal relationships could have been handled better. I've had some difficult relationships and I'm disappointed I didn't do better with some of those.

As far as technical failing, I gave [UFC bantamweight] Alex Caceres the wrong game plan when he fought Francisco Rivera [UFC Fight Night, June 2015]. I wanted him to be more aggressive than usual and it cost him the fight. I should have let Alex be himself. He likes to move around and get the feel of things. We were trying to get him to be a little more aggressive. I have to put that one on me. That loss sits right on my doorstep.

Mike Winkeljohn, Jackson Wink MMA

I let a fighter take a fight when there were a lot of family issues causing that fighter a lot of stress. That fighter should have never taken the fight. They weren't themselves. When I look back on it, it would have been better to not take the fight at all. I thought it was going to be able to be contained, but it wasn't.

During fight week, in the locker room warming up, you can tell sometimes when a fighter is on it or they're overthinking it. Lots of fighters get very, very nervous -- well, they all get nervous -- but some get really quiet. Some start making jokes when they weren't making jokes before. It's always something different. And on that night, I noticed the change in this fighter.

I was mad at myself, of course. In this case, because of how close I was with the fighter, I could have talked them into not taking the fight. At that point in the locker room it was too late. It was like, 'How do we fix this? How do we get this person out of their mental freeze?' Because they always talk about fight or flight, but the freeze part is gigantic in any situation around fear.

Michael Johnson's coach Henri Hooft says Nate Diaz "was playing with his head and he forgot to throw kicks." Jeff Bottari/Zuffa LLC/Getty Images

Henri Hooft, Combat Club

We all make mistakes in general. Maybe one that sticks out a little bit is when [UFC lightweight] Michael Johnson fought Nate Diaz [UFC Fight Night, December 2015]. We told him to kick the legs and he did early, but in the second round, Michael got a little too hyped up. Nate was playing with his head and he forgot to throw kicks. I was so busy getting him into the strategy, I didn't notice his entire head was getting out of the fight.

He started going toe-to-toe. Nate gets in your head and boxes so well. I could have done a little bit more in that situation, and I've learned from it. I feel like s--- about it. Michael was doing great in the first round, but when Nate gets you at the end of punches and laughs, puts his middle finger up, he's very good at getting you off your game. Instead of sticking with what he wanted to do, Michael fought Nate's fight and I couldn't pull him back. There was too much emotion.

As a coach, you always want to be capable of getting into your own fighter's head, even in circumstances like that.

Brandon Gibson, Jackson Wink MMA

My biggest regret is not being able to do more. Not for one fighter in particular, but for all my guys -- be at every single strength and conditioning, sparring, wrestling, grappling session. Just really be that coach who can give 100 percent to every fighter.

One of the mistakes I've made is trying to take care of too many fighters and drawing myself too thin. Especially some of these big camps, I think our coaching staffs are not that big and we always have important fights coming up. I've scaled back the amount of fighters I train, so I can give more to the ones I do train. And build up new coaches who can work with the next generation of fighters in our gym. I would say, annually, in 2015 I cornered 20 different UFC fighters. In 2017, I'm probably going to corner between six and eight.

Duane Ludwig, Ludwig Martial Arts

I don't want to reiterate the error, but just making sure I am mindful of my words to the media because they have power.

I did an interview where I was trying to highlight [UFC bantamweight] TJ Dillashaw's work ethic and commitment to being a champion -- that he pursued it with the most intensity of anybody I've ever seen -- and I needed to be mindful of what effect those words may have had on others I've worked with.

That was my fault and I still feel bad about it. I'm getting better at interviews as time goes on. I've realized the impact media has and the things they like to jump on. I've become more aware of what they're looking for and how I need to be mindful of how I word things.

Justin Buchholz, Team Alpha Male

I don't know if I have one "biggest mistake" for my career, but one I think about all the time is [UFC featherweight] Artem Lobov's physicality and how I didn't factor that into that fight with Teruto Ishihara [UFC Fight Night, November 2016].

I looked at the breakdown of martial arts skill, and Ishihara was going to win that all day. But I didn't realize how big Artem was until I saw him. So, you've got this crazy Russian-Irish guy, the fight is in Northern Ireland, and that's just one thing from a strategy standpoint we didn't factor in.

Artem is not a technical fighter, but he's 170-pound guy by the time he fights. Ishihara is real small for that division. I feel like if we would have had a strategy better prepared for a 170-pound, Ninja Turtle-headed Artem, instead of a technically inferior 145-pounder, we would have done a little better.

Firas Zahabi of Tristar MMA says he has "over and underestimated opponents" in the past. Jeff Bottari/Zuffa LLC/Getty Images

Firas Zahabi, Tristar MMA

I don't like to give that stuff too much attention. I like to learn from my mistakes but I don't like to glorify them or focus on them. I find that's a great way to repeat them.

I would say, though, that sometimes I have over and underestimated opponents. It's very difficult to estimate how hard someone will be to take to the ground. You see who has taken them down in the past and who hasn't, try to predict off their track record, but MMA math is not always perfect. A lot of times it comes down to styles and decision-making and things you can't equate before the fight. I try not to predict too much how good someone will be in any particular area.

John Kavanagh, SBG Ireland

Maybe not a very good one, but I regret my first 10 years or so of MMA and grappling with people a lot heavier than me. I'm now left with a pretty serious neck condition that means my own ability to grapple is severely hampered. One wrong move could have me off the mats, in pretty severe pain for months. This has already happened a few times. I take comfort that I'm still able to demo and coach and use lessons learned on next generation, but I miss the mat.