It’s easy to decide to create a new habit. It’s a lot harder to turn that decision into a lasting habit.

Partly, that’s due to the nature of habit formation. Most of us decide to create a strict routine, an approach that rarely works. In a study published in Management Science, the research team enlisted people who wanted to exercise regularly and assigned them to one of three groups:

The first group was asked to designate a convenient two-hour window, then follow a strict routine. (Something along the lines of “exercise at 6 p.m. every day.”) Every time they worked out they received a financial reward.
The second group followed a flexible plan, working out whenever they wished. They also received a financial reward every time they worked out.
The third group, the control group, was simply “encouraged” to work out more: no routine, no plan, no pay.

Unsurprisingly, people in both the “routine” and the “flexible plan” groups exercised more often than those in the control group. (Money talks.)

Surprisingly, though after four weeks — when the exercise habit was theoretically established, and the researchers stopped paying participants — people in the flexible plan group were more than twice as likely to keep working out than people in the strict routine group.

Why? The more rigid your routine, the more likely your routine will be disrupted, and the less likely you are to adapt. Miss your 6 p.m. workout and you’re unlikely to try to squeeze it in at 7 p.m.

For the flexible group, exercising wasn’t tied to a specific routine or time. Sometimes they worked out when they planned. Other times they worked out when they could. Or they squeezed in a shorter workout. They wanted to exercise, and taking a flexible approach gave them latitude to figure out how to make it happen.

Want to build and maintain a new habit? Step one is taking a more flexible approach.

But don’t stop there. According to a 20-study meta-analysis published by the University of South Australia, a few consistent behavioral patterns separate habits that stick from habits that don’t:

Energy. Makes sense. Decision fatigue is the enemy of new habit formation, as is overall mental and physical fatigue. Whenever possible, plan to do whatever it is that you want to become a habit when your energy level is higher.

Setting. Choice architecture is important, but so are visual and environmental cues. It’s “easier” to work out in your home gym than it is in the living room. It’s “easier” to make a few calls from your office than it is from your kitchen table. Habits are patterns, and the more supporting patterns you create, the better. A study published in Current Directions in Psychological Science found that many habits are triggered not by intention, but by environment or context. I make the bed because I got out of bed. I grab a protein bar and water because I walk by the kitchen on the way to the table where I work. I start writing because that’s what I do when I open my laptop.

Simplicity. Things that are easy to do are, um, easier to keep doing. That’s why habit stacking is so effective; once you’ve created a new habit, adding a small habit to the initial habit is relatively easy. (As an added bonus, the spillover effect also makes creating new habits easier.)

Choice. Here’s the biggie. The University of South Australia study found that behaviors people chose for themselves were much more likely to become habits than behaviors chosen for them. Extrinsic rewards, peer pressure… helpful, sure, but the best way to create a new habit is for you to determine the habit you want to create.

Bottom line on new habit formation? First, choose something you want to do: not just the goal, but the behavior that supports that goal. (If you want to get in better shape, don’t blindly embrace someone else’s program; choose the forms of exercise you are most likely to, if not enjoy, at the very least stick with.)

Then create a reasonably flexible plan, not a rigid routine. Say your goal is to drink 100 ounces of water a day. Don’t wait until the evening to try to catch up with your daily goal. Try to drink at least 30 to 40 ounces of “random” water, say, before noon.

Then let your environment help. Keep a bottle of water on your desk, and refill it as soon as it’s empty. Keep a full glass of water on the kitchen counter. Make it easy.

And keep it simple. Always drink water with breakfast. Always drink water at lunch and dinner. That’s an easy routine to follow.

And finally, make sure drinking more water is something you want to do, not just something you think you’re supposed to do.

Because if a goal is not your goal… the behaviors that support that goal won’t become habits.