Do you have a to-do list? Of course--most of us do. But what about a not-to-do list? It turns out that's at least as important, according to productivity experts. 

What exactly is a not-to-do list? It's not a list of bad habits you're determined to break or negative behavior you want to be sure to avoid. It's a list of tasks that you might think you should do, or might want to do, or might be asked to do by someone else. But because these tasks don't move you toward any of your larger objectives, don't feed your soul, and aren't necessary for you to do, you are much better off not doing them. They should either be left undone or you should delegate them to someone else.

The most successful people I know say that great careers arise out of what you say no to. It makes sense because time and energy is a limited resource for each of us and how we choose to spend that precious resource matters a lot. Management consultant and executive coach writes in the Harvard Business Review:

Once you accept that you have more to do than time to do it all, that is actually a liberating concept. This realization forces you to acknowledge there are lower priority items that you will likely never complete. Delete those non-essentials, put them on your not-to-do list, and commit to letting them go. This will prevent you from wasting precious time continually re-evaluating whether you might get to them that could be better invested in actually completing your work.

A not-to-do list will bring you clarity and peace because there will be less shame and anxiety over things you think you should do, or worse, have told someone else you will do, but are having trouble getting to. It will also bring greater transparency and improve your relationships with your colleagues and customers because you will no longer be making promises you can't keep.

It may sound counterintuitive--you're busy enough already--but set aside a little time, half an hour at least, for creating your not-to-do-list. The productivity you gain will be well worth it. Here's how to get started:

1. Assemble a general list of candidates for your not-to-do list.

If you track how you spend your time (which is well worth doing), review your records to see what tasks you're spending time on each day. Look at your calendar and any notes you may have that will shed light on exactly how you spend your work time. Anything you're spending time on that doesn't directly align with your long-term goals and vision for yourself should definitely be a candidate. So should items that have been on your to-do list for a long time, nagging at you, but that you have yet to accomplish. Things that other people ask you to do should go on the list of potential candidates, unless they move you toward your own goals. And finally, any task that makes your heart sink just to think about should be a candidate for your not-to-do list.

2. Ask yourself some questions.

Once you've got your potential candidates for the not-to-do list, challenge each of them with a few questions. First ask, "Will this task help me accomplish my goals and contribute to my vision of success?" If the answer is no, follow up by asking, "Will I or anyone else suffer meaningful negative consequences if this task doesn't get done?" "Is this task either urgent or important?" If the answer to these last two questions is also no, that task should go on your not-to-do list.

If something does seem urgent or important or could have negative consequences if it goes undone, ask yourself this: "Do I have to be the one to do this task? Or could I give it to someone else by delegating it or outsourcing it?" If there's any way to give this task to someone else, it should go on your not-to-do list.

3. Prepare some answers.

The whole point of the not-do-do list is so that you will be willing and able to quickly say no to tasks that don't fit your long-term goals and don't need to be done by you. As new tasks get added to your not-to-do list, it's useful to be ready with some quick answers in case anyone (including yourself) asks you to do something that doesn't fit with your mission.

Life coach Blaz Kos suggests actually preparing boilerplate text that you can quickly grab and drop into an email if you want to politely decline a request that you do something. You may also want to write scripts you can use in person or over the phone and come up with some things you should also be prepared to tell yourself whenever a non-essential task rears its ugly head.

4. Repeat.

As you're invited to take on new tasks, or as you come up with new ideas that you want to pursue, test each one against the questions above. Does it meet the very stringent criteria to be placed on your to-do list, or does it belong on your not-to-do list? Be vigilant about protecting your own time and energy and use your boilerplate or script to turn down tasks as needed.

Review you not-to-do list periodically--at least once a quarter, Kos suggests. As you get the hang of it, you may want to add more items to the list. Who knows? Maybe someday your not-to-do list will be longer than your to-do list.