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None of my three university degrees focused on economics. But there’s one economic principle that I learned early and use every single day.

That principle is opportunity cost.

In all my various life roles—husband, father, friend, community volunteer, leader, consultant, executive coach, etc.—I’ve made who knows how many thousands (millions?) of decisions on how to invest my time, energy, and other resources. Like everyone else on the planet, I have finite “bandwidth.” I can’t accommodate every request from people who seek my help or attention. I can’t accommodate every activity that I’m tempted to put on my own to-do list.

Here’s the reality: every single thing I say “yes” to carries an opportunity cost. In other words, I could be doing something else instead.

Like many other people I know, I have a tendency to get swept up by causes I care about. My gung ho default is to say “yes” and then get on with the planning and execution. But if I’m not careful, I end up saying to myself, “what was I thinking?” Worse yet, my “yeses” sometimes keep me too busy to focus on what really matters to me.

I’m not suggesting that a knee-jerk “no” should be our default response, certainly not to requests from people who are most important to us. But I am suggesting that a mindful assessment of how we use our time can both preserve our energy and boost our overall effectiveness.

Some helpful ideas on that score can be found in When to Say Yes by Don KhouriHe holds a PhD in human and organization systems and an MBA in organizational behavior. The tips he offers are backed up by solid research and real-world experiences.

Rodger Dean Duncan: You quote serial entrepreneur Tal Gur as saying “Effectiveness is about the ‘what,’ not the ‘how much.’” How does this apply to your approach to personal productivity?

Don Khouri: The key reason leaders end up with too much on their plates is they don’t have a clear decision process for evaluating requests for their time. People don’t like to say no, and many end up saying yes even when they want to say no. If we can all get more focused on the right yeses, it will be more about the “what” and not “how much.”

Don Khouri

Duncan: Typical to-do lists, you say, are part of the problem of busyness rather than the solution. Please explain.

Khouri: There are several problems with to-do lists.

One, they don’t tell us what we need to do next. If you have 50 items on your to-do list, which one will you do first?

Two, they include items that can’t actually be completed. When you see the complexity of the action that you need to complete, you have to take time to break it down and figure it out. What you need to do in that moment is make a decision about the action required to make progress on that activity.

Three, the items we put on our to-do lists are not necessarily actionable. The easier we can make it for ourselves to know the action, the easier it will be to execute it at the appropriate time.

Finally, to-do lists are usually not prioritized. When we look at an unprioritized list, we need to make decisions in the moment on which task to focus on first. Sometimes we get lucky and choose the right one. At other times we choose the easiest one or the thing that is the most actionable.

Duncan: A lot of people sing the praises of multitasking. But you say multitasking doesn’t work. Why?

Khouri: The research is clear on this. We think we can multitask, but we can’t pay attention to more than one thing at the same time. It takes us longer to complete two tasks when we try to multitask than if we had completed them one after the other.

Duncan: What do you see as the keys to being purposefully productive?

Khouri: Being purposely productive is feeling in control, crystal clear on your goals, making progress on your most significant goals, and being conscious about how to invest your time.

Duncan: What are some of the most common roadblocks to making good decisions?

Khouri: Humans have these things called cognitive biases that get in the way of making good decisions. The most relevant one that gets in the way of productivity is the planning fallacy. This says that we believe we can do more in a given amount of time than we actually can. Even when we are aware of the planning fallacy, we still underestimate how much time something will take. The good news is that it only applies to our own projects. That means we can ask someone else who is knowledgeable to help estimate a project or a task, and that will be more accurate.

Duncan: Decisions on how to invest our time are influenced by what you call the “relationship hierarchy.” What is that, and how does it work?

Khouri: The most productive people have a relationship hierarchy where requests from people at the top of the list will get more consideration than someone lower on the list. We all have one, and for some it is more conscious.

Duncan: How can people most effectively “assess the quality” of requests for their time?

Khouri: If the request is respectful of your time, necessary, well thought out, clear and concise, and includes solutions, then it is a quality request. The most productive people expect requests for their time to be quality requests. Otherwise, they refuse it.

Duncan: What’s the best way to challenge—or respectfully reject—a request for your time?

Khouri: I don’t talk much about saying no because there are so many great resources out there already.

Here are three simple solutions.

One, “Absolutely, what should I deprioritize so I can focus on this new request?”

Two, “I’m not able to take that on right now, but Joe will be a great choice for it.”

Three, “I’m not able to take that on right now due to other priorities. Let’s revisit in six months.”

Duncan: In a nutshell, what seems to be the mindset of the most productive people you know?

Khouri: They are conscious about requests for their time and the trade-offs of saying yes. They make sure a request aligns with their roadmap, they assess who is asking, ensure it is a quality request, prioritize and reprioritize if necessary, and they master delegation.

Duncan: It’s been said that delegation is the key to executive sanity. What do you see as the steps to effective delegation?

Khouri: Yes, the most effective leaders have mastered delegation. Ask yourself five simple questions when delegating a new project or task—

  1. What does an outstanding result look like?
  2. Why is this task or job important?
  3. How will you support this person to be successful?
  4. Who will be held accountable?
  5. What’s in it for them?

This column was first published by Forbes, where Dr. Duncan is a regular contributor.