A science-backed 21-day program to be happier, healthier, and more successful

Mike Nudelman / Business Insider

So you want to be happier, healthier, and more successful in 2016?

Faced with unlimited advice and little time to spare, it's hard to know where to start.

#BIBetter is a 21-day self-improvement program designed for the busy professional, featuring a few habits that will make a big difference and a bunch of tasks that most of us have been putting off for too long.

We recommend participating with at least one other person, so you have more fun and keep each other in check. You can start on any Monday and should complete actions on their specified day when possible.

The following slides go through the days and the science behind them in detail. You can also reference our infographic calendar.

MONDAY, DAY 1: Floss your teeth. Do it every day for the rest of your life.

Believe it or not, as many as 50% of Americans say they don't floss every day. If you are one of those people, then make today the day you start doing it consistently.

How can you get in the habit?

Stanford psychologist B.J. Fogg is one of the foremost researchers on habit formation. The takeaway from all his work: Floss one tooth.

As in, if you're trying to form a habit, it can be helpful to start as small as possible, with a minimum viable habit. The point, Fogg emphasizes, is to insert the structure of the activity in your day, rather than doing it perfectly every time. This way of thinking works for all habits, and it works for flossing, too — and if you floss the whole mouth, then you're doing even better.

Indeed, this core dental hygiene technique will clean your teeth and gums of plaque, protecting your teeth as you age and saving you on dental bills. Some studies have even found that flossing is associated with a lower risk of heart disease, diabetes, and dementia.

TUESDAY, DAY 2: Break a sweat. Do it every day for the rest of your life.

For a wide range of ailments, exercise is an almost magical cure, which "can improve memory and concentration, lessen sleep disorders, aid heart disease by lowering cholesterol and reducing blood pressure, help sexual problems such as erectile dysfunction, and raise low libido," notes Slate.

Just a little bit of exercise has huge benefits. Research shows that running just five to 10 minutes a day can add years to your life, and if you establish that minimum habit now of doing at least that, you can build on it. A seven-minute workout using interval training can make a huge difference.

Longer workouts are obviously great, too.

Think you're too busy to work out? Tell that to GE CEO Jeff Immelt, who gets up at 5:30 every morning for a cardio workout; or Xerox CEO Ursula Burns who has an hour of personal training at 6 a.m. twice a week; or Twitter and Square CEO Jack Dorsey, who gets up similarly early to take six-mile jogs; or Starbucks CEO Howard Schultz, who likes to ride his bike every morning.

WEDNESDAY, DAY 3: Write in a journal. Do it every day for the rest of this program.

Psychologists have been studying "expressive writing," or journaling about difficult moments in your life, for a few decades. They've found that a few minutes journaling improves everything from mood to immune system to sporting performance.

It works for work, too: A Harvard Business School study found that people who wrote about their jobs improved their performance by 23%.

"When people have the opportunity to reflect, they experience a boost in self-efficacy," says HBS professor Francesca Gino. "They feel more confident that they can achieve things. As a result, they put more effort into what they're doing and what they learn."

So as a part of this life-improvement adventure, we're asking you to reflect on your day, plus on whatever journeys we send you on. You should also take the opportunity to look at the tasks that lie ahead and start making plans for the ones that require preparation.

If you find journaling to be useful, then we encourage you to keep it up for the rest of your life.