It used to be that you could deduce what someone was doing based on where she was. Sitting in an office typing? Probably doing work. Camped out on the bleachers during a soccer game? Must be off the clock.

But now at 10 a.m. on a Tuesday you might be Facebooking your old college roommate. And at 10 p.m., you could be in a bathrobe and clay mask conducting serious business (while catching up on reality TV).

Thanks to portable technology and a shifting work-life landscape, duty and play have become strange bedfellows -- and not only because you occasionally fall asleep next to your laptop.

We're all living in a permanent state of Elsewhere, says sociologist Dalton Conley, author of "Elsewhere, U.S.A." Conley, who coined the term "weisure" to describe this hybrid of work and leisure, says that since we're physically able to work around the clock now, we often feel we're in the right place only when we're in two places at once.

This doesn't mean we're doomed to 24/7 enslavement, however; we just have to figure out a new way to work -- and we need a new set of rules for work-life balance.

The idea that we can and should work for hours at a time goes against our biological wiring: "Everything in nature is oscillatory," says Jim Loehr, Ed.D., author of "The Power of Full Engagement"; sunlight, seasons, even our sleep patterns move through cycles. "If you spend too much time in the hot zone, you're in trouble."

Rather than seeing your day as two chunks (before lunch and after, or more likely, at the office and at home), start to plan your work in one-and-a-half- to two-hour blocks. A 15-minute pause every few hours is critical. Without it, you erode your ability to catch errors and snuff out that creative spark that invites insights.

You'll get your biggest bang out of a rest period if you're active. Moving forces you to use your motor cortex, giving your prefrontal cortex time to recover -- which is why if you're still for too long, you'll make poor decisions and even feel emotionally flat.

Your brain craves novelty, so switch to different tasks as your energy levels ebb and flow. "I call it one-, two-, and three-level thinking," says David Rock, author of "Your Brain at Work." "Level one is the surface stuff (deleting emails, for instance). Level two requires a little more focus. But level three, the deeper thinking, is what we need more of. It involves writing, creating, planning, and strategizing."

You can do your best level-three thinking first thing in the morning or when you're fresh from a break. Bar distractions as much as possible. Even just 30 interruption-free minutes, Rock says, can make you much more productive.

When your energy's waning, a shot of something funny or novel can raise your levels of dopamine, which you need for clear thinking, and encourage new connections in the brain.

A study from the University of Melbourne found that workers who surfed the Web for fun (less than 20 percent of their total work time) were slightly more productive than those who didn't.

(Need a break now? Browse this gallery of pets in costume!)

Psychiatrist Daniel Siegel, M.D., author of "Mindsight: The New Science of Personal Transformation," says that to experience true leisure, we can't just zone out in front of the TV. "Leisure sets the stage for creativity and novelty, which research suggests can keep the brain young," he says.

Immerse yourself a few times a week in non-goal-related activities, such as visiting a museum, going to a park, taking a hike, or even just wandering a bookstore with no agenda except to open you up to new insights and connections.

If there's one natural boundary worth shoring up, it's between waking and sleeping. Choose a cutoff time for checking email. Then stick to it.

Don't conserve energy by cutting back on your relationships. "A CEO shared with me recently that his 5-year-old son said of him, 'I don't think my daddy likes me very much,'" says psychologist and author Jim Loehr. "'He's always tired when I'm around.'"

That man learned quickly that if you don't invest in your relationships, Loehr adds, you'll get no return. And in the end, the people we love deserve the greatest gift we can give them: the unfettered power of our attention.