Robert Seo on patrol during the invasion of Iraq. Robert Seo As a Marine, Ironman Triathlon participant, Wharton Business School graduate, and co-founder and co-CEO of tech startup Slidejoy, Robert Seo knows something about success. And he learned the most important lessons about how to succeed from his time in the Corps.

"If there's anything that I got from the military," Seo told Business Insider, "it's that I don't have any limits. The limits are what I set for myself."

Seo's proven it. Having "run away" from undergraduate work to join the Marine Corps, Seo served in the invasion force's vanguard during the initial push into Baghdad in 2003.

After completing his service, Seo received a BA in economics and a minor in mathematics from the University of Maryland. He went on to take part in an Ironman Triathlon to raise funds for the Jericho's Veterans Initiative in South America, before working a quick stint at Goldman Sachs and receiving a double major from the Wharton School in Entrepreneurial Management and Finance.

After graduating, Seo decided to embrace the inherent risk of launching a new company and co-founded Slidejoy.

"To make that step into entrepreneurship is scary," Seo said, "but it was something I had to do."

Slidejoy is a mobile application that presents targeted ads on cell phones' lockscreens. Users can swipe left or right on the ad, choosing to engage it or ignore it. Whatever the choice, the user earns money, and the advertiser gains exposure.

"You look at your phone 50 to 100 times a day," Seo said. "That view is so so valuable. And you do it all the time. Having access as an advertiser to that screen is huge."

Seo told Business Insider that his run of success hinged upon five lessons he learned in the military:

1. Happiness is a choice

During the invasion of Iraq, Seo realized that happiness depended on his attitude at a given time. Although he was homesick and in a difficult environment, Seo could still choose how he felt in any given situation.

"You make that choice to be happy," Seo said. "I chose not to think about the things at home that I missed. Instead I would focus on the things that I have here."

2. A successful team values itself more than the individual

"The importance of brotherhood is something I've been able to bring onto Slidejoy. I'm not just looking for world-class talent, which we have. I know how to recognize people who are great at what they do, but also have the selflessness, that dedication to something bigger than themselves."

3. You have to learn how to be truly courageous

"For anybody out there, for anyone who wants to take a big step, they're not that special. We're all the same. Courage isn't not being scared, but instead recognizing that it is the ability and fortitude to move forward in the face of fear."

4. Anti-fragility is key

"Fragile people break and crack under pressure. Resilient people will bounce back from failure to the same level they were at before. Anti-fragile people will take those setbacks and bounce back harder to a new level. I think that anti-fragility is something you need as an entrepreneur, and that is something I learned in the military."

5. Live with a sense of purpose

"No matter what I do, I will live my life to its full potential ... That sense of purpose is what drives me today. Being able to find the right people you're happy with and being able to find that purpose that makes you want to give your all is what drives me. It should be something that everyone looks for."

Slidejoy has gone on to win first place in the Wharton Business Plan competition.