Staying fit at 50 isn’t always easy. You have more pain in your joints, you can’t lift quite as much as you used to, and finishing workouts is tougher.

It’s even harder when you’re the CEO of a company, a published author, and consulting Fortune 500 executives on crisis-level decisions, but Eric Schiffer doesn’t let that stop him. In fact, he’s feeling stronger than ever.

“If anyone says you can't stay in shape as you get older, that's craziness,” Schiffer tells Men’s Fitness. “I point to my friend Frank Zane, who I've trained with over the years. He taught me a lot about training and taking care of your body. I think now, as a 50-year-old Gen-Xer, I'm in some of the best shape I've ever been.”

Schiffer is a busy man, but he still finds time to get in the gym and work out. Schiffer is CEO and chairman of the Patriarch Group, a private equity firm in technology and media. He also has appeared on television as a commentator on CNBC, Fox, and CNN. (Here’s a recent Schiffer appearance on the management future of Uber for CNN International.)

Schiffer, who is dating Dr. Jenn Mann of the VH1 reality television series Couples Therapy and has published books on business leadership and management, started seriously training when he was a teenager, and that mentality is paying off by helping him stay fit decades later. During those years, Schiffer wrote a book for kids interested in bodybuilding, Pumping Iron for Teenagers, and got former champion bodybuilder Franco Columbu to write the foreword.

“I wanted to be able to teach kids my age how to do what I was doing back then,” Schiffer said. “I wrote the manuscript in two weeks, got an agent, and within six months I had a deal with Ballantine Books. The training really helped me in sports and from a confidence standpoint, and it’s built a foundation for how I train now.”

Schiffer spoke with Men’s Fitness about his daily workout routine, tips for staying confident as you get older, and more.

What’s your workout routine like? How has it helped you stay in shape as you get older?

When I was young, I tried to learn the best and most efficient techniques and carry them with me. It helped me be a better athlete in high school, it led me into contact fighting in my 20s, and now I feel like I’m in some of the best shape of my life. I typically start on the major muscle groups, and I’ll do this twice a week or so. The entire workout is intense, and I try and keep each set like that. I work downwards. I may take the weight down 25% as I go. I go to failure, I’ll do a couple forced reps, and then rest periods for 30-45 seconds. I do five sets per exercise and I typically do about 4-5 exercises per body part. I’ll do bench press, dips with weights, flyes, cable or free weights, and decline and incline chest presses.

What types of training do you like to do? How do you develop your programs?

The important aspect of training that leads to growth is the combination of the time-based intensity (so, not resting), the forced reps, and the downward weight stress. When your muscle goes into failure, you can get a little bit of recovery. You force-rep it down. Then it's pretty much shot at that level of resistance, but you can hit other fibers that aren't called upon at that higher level that you will hit on the lower levels. I believe there are various degrees of fibers, and that the only way to hit them all is to de-escalate and hit them through forced reps. It works quite well for me.

What’s your diet like, and how do you handle your nutrition?

In some ways I think the food side is probably as important as, if not more important than, the training side. The mind is a weapon for success, and I wanted to maximize that instrument by keeping my body in as good of shape as I could. I decided to focus on a plant-based diet. At first, when I did the research, I thought "You know, you can't be on a plant-based diet and still maintain muscle and really be strong and have the same power." But that isn’t true for me.

What advice do you have for guys looking to boost their confidence in the gym, at work, or just in their own lives?

I think the No.1, to me, it's critical that you have certainty about yourself and what's possible for yourself. I think it all starts from a feeling of certainty. I think you can develop certainty as a habit by just beginning to be aware of things that you know are certain in your life. Arnold Schwarzenegger's a master of programming himself. He programs himself for success. I program myself for success, there's no questions.

Part of that is thinking out in the future about how I'm going to behave in certain ways. Then connecting that feeling of certainty to the behaviors I will do in the future. If you want to achieve certain things, you always want to break it down to the specific behaviors necessary for achievement and the specific tasks. That will start to build confidence in yourself. Then you start to get a feedback loop, because you start watching yourself do the tasks.

When did you first get interested in bodybuilding and training?

I started training at an early age, and really got into it. By the time I was 13 or 14, I had already developed some muscle and it really made feel good while playing sports and just overall. [A little while] after that, I went with my parents on a trip to Europe. I didn't want to go, and they kind of forced me to go, and while I was there I got the idea that I wanted to write a book and I wanted to show kids my age that they could train and start taking care of themselves at a young age.

How did the book come together?

I ended up locking myself in a room for two weeks, as writers do, and I went to work. I literally had a manuscript done in a couple of weeks, I called around and got an agent, and within six months I had a $10,000 advance from Ballantine Books. I called up Arnold Schwarzenegger via a connection from my family, and we talked, and he helped me get to Franco Columbu to write the foreword to Pumping Iron for Teenagers.

What are some things younger guys can do on a regular basis now that will help them down the road? What’s the best way to form those potentially long-term habits?

You have to start with a goal. What does the body want and why? What are the reasons you want it? List them. Start from the macro all the way down to the micro. What's it going to give you in terms of your overall life? What's it going to do in terms of your relationships? How's it going to make you feel about yourself? What's it going to do for your confidence? You start macro, all the way to micro. Get clarity about that goal. Then really visualize it. Some people use tools where they'll take pictures of bodies that they like that they want to look like. That can work. It certainly worked for me when I was younger.

The clearer the vision is, it begins to program your body that this is the path that it's going to be going on. Then, the second piece is the motivational factor. Write it down. Make a commitment as to this is the body you want by this time period. This is what you're willing to do to make it happen. What's the price you're going to pay? Commit to it in writing. Hold yourself accountable. Set a goal for the month and the days that you're going to train.