DUBLIN -- Sometimes life is less about how you handle failure than about how you handle success. Do you let that success go to your head? Do you take a breather and relax and have trouble summoning the hunger you had that led to those good moments in the first place? It’s a natural tendency, and not just in sports, but everywhere, in your career or mine.

It’s especially hard if you’re the U.S. men’s national team and you had a good World Cup, advancing from a difficult group in a way that few had expected, and now you have to deal with a World Cup hangover, playing in games with lower stakes.

But that’s what we’ve seen from the U.S. since the end of the adrenalin rush that came with all the moments in Brazil 2014 that none of us, including the players, will ever forget.

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The U.S. lost 4-1 to Ireland’s second-choice team on Tuesday, a dismal end to a calendar year that in the big picture has to be seen as positive, given the World Cup performance, but that concluded with just one victory in the final eight games. There was talk after the game of “growing pains,” as U.S. coach Jurgen Klinsmann put it, the inevitable issues that arise when you bring young players, some of them teenagers, into the national team for the first time.

But the bigger issue for the U.S. right now has nothing to do with growing pains and more to do with answering the question: How do you handle success? Nine of the 11 U.S. starters on Tuesday were on the World Cup team. They were the players who struggled the most, not the youngest guys.

“We had some guys who were at the World Cup today, and we weren’t there,” said forward JozyAltidore, who served as captain in the absence of Clint Dempsey. “We weren’t there in a lot of places on the field. It’s growing pains, but for some of the older guys it’s unacceptable, including myself. Those kinds of things can’t happen.”

“We just didn’t come to play today,” Altidore added later. “And it’s been a trend the past few games.”

“I feel like it’s something with our mentality maybe,” said midfielder Alejandro Bedoya. “I don’t know what it is. I can’t really pinpoint it. The last four games I feel like we’ve had results in our hands, had the game in our control, and we let it go. Whether it’s teams equalizing late or like tonight, when they scored the second goal and knocked the air out of us. You’ve just gotta pick it up.”

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​For years, the U.S. has had a tendency to play better at World Cups when less was expected of the team. But when the expectations rise, as they did after Brazil, the U.S. has often underperformed. And right now those doing the underperforming are the players who were in Brazil. Emotionally and physically they are spent, or not far from it. And it’s equally an issue for MLS-based and European-based U.S. players.

“They have to learn emotionally how to digest a World Cup,” said Klinsmann after the game. “A lot of our players had big problems digesting those extreme emotions. They dropped 20, 30, even 40 percent in performances in their club environment. Many of the Europeans lost their starting spot ... They didn’t know how to deal with all these emotions and all the recognition and all the compliments after the World Cup.

“In a certain way it’s human. It’s understandable.”

Klinsmann sees it as a challenge for himself, too. “How do you manage the roster coming out of the World Cup with all the emotional things that happened in our country and get these players back on track?” he said.

He didn’t say it, but this is something new for Klinsmann too, at least as a national team coach. His term as the Germany coach ended after the emotional high of the 2006 World Cup, and he didn’t have to work his way through the challenges that followed that tournament with the German national team. Yes, Klinsmann had to learn how to handle success as a player, but doing it as a coach isn’t the same thing.

For now, one of Klinsmann’s solutions in 2015 is simple: Be tougher.

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​“A lot of the work down the road will be done for us off the field,” he said. “We have to educate the players better. We have to guide them hopefully with more influence in their club lives. We have to make it clear that they have to go through pain, they have to get tougher.”

“When I used that word two, three years ago—we’ve gotta get nastier—some people were very critical of me. How can you say that? But I’m telling you that again: We have to get nastier. It’s just normal. It’s not a negative word. We have to become more physical, we have to be dominant and send signals out all over the field. It took us 70 minutes until Jozy got the first yellow card for a foul he only did because he was fouled before that. It’s the international game.”

Perhaps there’s something to that. Maybe it does come down to some of the bare essentials like being more physical. But learning how to handle success—as a coach, as a player—is about more than that. A World Cup year has now ended. It had more good than bad in it for the United States. It left you wondering about what this team could achieve in four years.

But the end of 2014 also leaves you wondering if the success from Brazil is sustainable under Klinsmann. And that will be a challenge for everyone involved in the national team program, including the coach.