Have you ever started a new habit with a lot of enthusiasm and built up some great momentum? Maybe you were able to workout three times a week for an entire month. It feels great, and every day you stick with it you're strengthened to continue tomorrow.

But then something happens. You have to go away to a wedding a long weekend, or your kids both get sick at the same time and force you to drop everything to care for them.

Your momentum is broken, and when things settle down you find yourself ordering takeout and skipping your workout to watch the latest episode of The Voice (it's cool, I won't tell anyone).

Momentum can be both a blessing and a curse. When it's on your side you feel amazing and it becomes a catalyst for even more positive behaviors. When it's against you it somehow saps the motivation out of almost everything you do. I call this lazy couch momentum.

To avoid succumbing to the lazy couch momentum I follow one simple rule:

Don't Skip Two workouts in a row.

We all have days when you're too tired/grumpy/stressed/upset to stick to your normal schedule, and that's totally fine. Take a load off. You deserve it (even if you think you don't).

What you DON'T want is for it to become the new normal, and you can avoid this by not giving in twice and letting lazy couch momentum build.

This is one of the few times in your life when it is smart to muster up some willpower and just make it happen. No excuses, just put on your sneakers and walk out the door.

You don't have to workout at full intensity if you don't want to. If you normally go for a run, just go for a walk if that will get you out the door. I don't care if you just go to the gym and stretch for 20 minutes. Just do something physical. Anything. You won't regret it.

What's important is that you don't let lazy couch momentum build. You take away its power by not feeding it consecutive victories, and before you know it you'll be back in your normal routine.

Once lazy couch momentum does build though, it is a lot trickier to free yourself. So it's best not to let that happen.

But what if whatever interrupted your routine lasts awhile, like an injury or long vacation? Obviously you shouldn't force yourself to exercise if it will hurt you in some way.

However the first week things are back to normal you should reinstate the Don't Skip Two rule. If before your interruption you had a routine of working out Monday, Wednesday and Friday, it's fine to take Monday off to recuperate without any guilt .

But get back in the saddle on Wednesday.

Again, this isn't about torturing yourself, it's about momentum. For that reason it doesn't matter what activity you do. Just Don't Skip Two workouts in a row.

You can use a similar strategy for other habits as well, like cooking or meditation. Simply managing your momentum by doing some version of your habit--like making some pasta from a box or taking a few deep breaths in a quiet place--instead of skipping it completely twice in a row can help keep your habit intact.