I started in mixed martial arts with one goal: to win a world championship. It was a promise I made to my dad, and it's the only promise I ever made to him that I have not kept. I have done everything in my power to keep the promise, and I got close a few times, but in the end I have always come in second. I'm still working toward my goal, though, and the promise I made all those years ago remains very much a motivation.

I think about that goal, that promise, every day when I go to practice. My body gets a little more sore now that I'm in my 40s, and it takes me a few more minutes to warm up now. But once I get warmed up, I go just as hard as I always have. I've been competing since I was a kid, first in wrestling and now in MMA. It's the only life I know.

Maybe I just fear the unknown, like everybody else, but I don't like to think about being done with fighting. It's a lifestyle -- going to practice, working hard, being with the guys, and even dieting and trying to make weight limits. Why stop? If I felt like I was slowing down at the gym or during matches, or if I felt like my goal of winning a world championship was out of reach, then yeah, I'd have a different conversation with myself. But right now I don't even think about stopping.

I did think I was done at one point. In 2014, I was facing a suspension and couldn't get licensed for two years. So whether I wanted to be done or not, I was kind of done. Two years seemed like a mountain that was going to be hard to climb.

At first, I actually felt a little relief. It was such an exhale after a lifetime of competing. I started doing TV commentating, and I really enjoyed flying to a new place every week and living in hotels. But after just a few weeks, I could sense that something was missing. I was bored. It's a lonely life, living on the road and eating dinner by yourself. I didn't know what to do with my time, which made me miserable.

If there's anything I hate in this world, it's a day off. People go on vacation, and I'm always very happy for them. But that would be a prison sentence for me. I do not want a vacation.

I knew I had to get back to the gym, be with the guys, wrap my hands up and go out and be part of something. So, for the rest of that suspension, I was in the gym every day. I competed in grappling contests, the only place I was allowed to compete. And as soon as the suspension ended, I signed a contract and had a fight to prepare for. I felt good about having my sense of purpose back.

The competitive urge never goes away; yet as much as I live for it, for a fighter, competition is filled with an anxiety that exists in no other sport. There's everything from fear to excitement running through you. I believe there's no one word that can fully describe the feeling. It isn't overly pleasant. You're competing not just with your career on the line but also your health and well-being. Fighting is a sport that's all about damage. You're trying to hurt the other person, and that makes it different from all other sports.

Sonnen, right, could potentially earn a Bellator light heavyweight title shot with a victory over Lyoto Machida on Friday night. AP Photo/Bebeto Matthews

I'm always amused when commentators celebrate athletes like LeBron James for dealing with stressful game situations. "This guy has ice water going through his veins." I hear that and I think: He's trying to have more points than the other guy when time runs out. How the hell would you be nervous about that?

There's another thing that bothers me about the way some people think about competition: Sometimes at a youth wrestling tournament I'll see a father who is coaching his kid -- which is always a disaster, by the way, but I digress -- and I'll hear him tell his 9-year-old, "Get fired up! You gotta get psyched up!" And I'll just be thinking, what the hell does that mean? How do you get fired up? How do you get happy or sad or angry? How do you get any emotion? It just happens, then you've got to deal with it.

As a competitor in fighting, you maybe learn over time how to deal with your emotions better, which in turn makes you better at what you do. But you have to understand that you're not in control. It's stressful to be in a fight. I'm happy to be doing this for a living, and I look forward to the competition, but I don't enjoy the nights when I have to fight, even though I've been preparing to do it all my life.

Being at the fights as a TV commentator is a completely opposite experience. Even though I'm a lot newer and less experienced at that than I am as a fighter, I feel totally comfortable at the microphone. Talking about fights just comes naturally. When I used to watch as a fan, back in the early '90s, I never watched alone. We had people over at the house, my dad did, or I'd be with my friends. We'd sit and talk about the fights as they were happening. So when I do that now, yeah, sometimes they make me wear a suit and tie, but aside from that, I'm just saying what I'm seeing, like I always have. I'm having an ice-cold Coke, some nachos sitting next to me, and enjoying the show.

I'm not ready for that to be my only connection to fighting, though. I still have my goal, that promise to fulfill. I thought I was on my way to a world championship when I fought Fedor Emelianenko last fall, but I fell short. Back in 2010, I had a chance against Anderson Silva. I did everything I could do to beat him, but I lost fair and square. For the most part, despite competing at the highest level against legends of the sport, those are negative memories. That's why I try not to look back. I mostly remember the bad stuff. I remember letting up here or messing up there.

Sonnen nearly reached his goal of becoming a world champion in 2010, when he dominated then-UFC middleweight champ Anderson Silva for four rounds before falling in Round 5. AP Photo/Jeff Chiu

The most positive memory I have in this sport is from a fight that probably nobody saw. It was on a UFC undercard 10 years ago against a guy named Yushin Okami. I was ranked No. 9 in the world at the time; he was ranked No. 2 in the world. I won, and afterward I remember thinking: If I can perform that way every time, I'm going to win most of these matches. I just felt right that night. I felt it in the back warming up. I felt it in the ring. Mentally, I kept my focus. That was the way I always want to compete.

You know who else was on the fight card that night? Ryan Bader. Now, a decade later, he has the Bellator heavyweight and light heavyweight belts. He owns the world championships that I need to have to keep my promise to my dad. And Bader is within reach. If I beat Lyoto Machida on Friday night, I'm going to fight for the title against Bader next.

I used to whip Bader in the wrestling rooms. He never got the best of me. So if that match does come about, I will have a good source of confidence and motivation.

But I can't allow myself to look ahead. Right now I have to remain fully locked on Machida. He is all I think about, all day long. At night, I get in bed and watch Machida tapes. I go to the gym and practice with Machida in mind. It's not easy, though, keeping to "one step at a time." I'm better at talking about it than doing it. And yet I know that if I don't keep my focus, I could get carried out after fighting Machida, like many guys have.

I'm very aware of the damage that fighting can do. This is a contact sport. Nobody said MMA is good for you. We do many things to keep it as safe as we can, but that's the best we can do: keep it as safe as we can. I've always taken precautions. In practice, for example, I have around 30 teammates and I'm the only one who wears headgear every day. I've done that for my entire career. And I also don't fight in practice. I know a lot of guys who do, and if I end up with a partner and he wants to fight, I stop going with him. I only want to practice and work out. I do my actual fighting a few times a year, whenever I can get a match.

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I'm going to keep going like this until I fulfill my promise or until the reality hits that I'm just out of time. When that day comes, I will focus on the other deal I made many years ago.

As a kid in Oregon, I had a great wrestling coach, Roy Pittman. I never paid him a dollar, never even thanked him, but when I was 9 years old I made a deal with him. His deal was: I will teach you what I know, and when you're done with it, you've got to go teach it to somebody else. So ever since I got out of college, I have coached kids' wrestling. I'm just honoring my deal. And I hope that the kids I coach will take the skills I'm teaching them and someday pass them on to somebody else.

I will not coach my own kids, though. I've seen that in action, and it never seems to work. I will expose my kids to a little bit of everything, see where their interests are, and then I will just be the chauffeur, making sure they're at practice on time. I look forward to watching them get into sports.

I see guys like Donald Cerrone and Max Holloway turn parenthood into a motivator for sustaining their fight careers. But I've seen other guys say, "I've got kids now, so I'm stepping away to go do something else." For me, fatherhood hasn't pushed me in one direction or other. It does change your perspective, for sure, makes you want to be a better person. In general, life is much better as a parent. Different things matter now. But the biggest impact on my fight career is that practice times have had to change -- I go on the kids' schedules, they don't go on mine. Still, in the end, Dad has to go to work.