Summer is upon us?--a time when millions of people flee their cubicles and take a much-needed break from work.

For many, however, physical separation from their office doesn't necessarily mean they've completely broken free from the obligations and pressures of their job. With your smartphone in your pocket, you're always just a tap and a swipe away from it all.

Incessant (or even occasional) checking and replying to email while on vacation, however, seems to defeat the point. How can you truly relax or connect with family and friends when your mind is still focused on project deadlines and conference calls?

Josh Leibowitz (no relation) was one of these distracted vacationers until a freak smartphone accident (he dropped it in the ocean, rendering him completely out of touch for three whole days). This led to some soul-searching and a fresh determination to make the most of his limited vacation days with his family.

There's an ironic twist to this story: As Chief Strategy Officer at Carnival Corporation, Leibowitz's very job is to provide enjoyable vacation experiences.

For the past five years, as he explains in a TEDx Talk he delivered recently in Coconut Grove, Florida, he has led extensive research into vacations. His teams have surveyed over a hundred thousand travelers across six continents, and they've talked to thousands of experts.

What did they learn? Not everyone takes all their vacation time. While this in itself is not surprising, the sheer numbers are: In North America, there were 662 million unused vacation days left on the table last year. "To put that into perspective, that's the equivalent of 1.8 million years of vacation time."

What did surprise his team was that many vacationers, even if they do take time off from work, don't know how to make the most of their days away.

In his talk, Leibowitz shares three pieces of advice for getting the most from your vacations, based on his own experience:

1. Set a goal.

As part of their research, Leibowitz's team conducted focus groups.

"As we watched these people plan their dream vacation, what struck me was that everyone started in the same pattern. They all started with 'Where should we go?' 'What are we gonna do?' 'Who are we gonna go with?'...No one started with the question of 'Why are we going?'"

Set a goal for your vacation. "This is the why. This is what matters. This is what's most important," says Leibowitz. "For me it was all about connecting with family. For others it might be about hiking in the Himalayas with total strangers."

2. Build a culture that supports time off.

"Seventy-five percent of people say that they work all of our part of the days they're on holiday. When you dig another layer underneath the research and you ask why are these people working...they'll tell you that their work cultures don't support taking time off."

"Two-thirds of the people told us that their bosses and their colleagues don't support their time off. So we need to take steps in our workplaces to support each other when we take time off, because time off makes you better when you return."

3. Make your personal why happen no matter what.

"Avoid your kryptonite. For me that was always checking in at work. For others it might be thinking about something back at home. But it's important to make it happen no matter what."

Leibowitz gives an example of how on a recent vacation he woke up a couple of hours before his family so he could get some work done. "I felt better because I had the things done I needed to get done and they felt amazing because we could enjoy our time together."