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I have been treating patients using cognitive therapies for almost 15 years, and one of the most successful exercises I have ever seen work to help them re-engage their sense of well-being is so simple that each and every time I convince someone to do it, I am still remarkably struck by how effective it is.

Before I share this exercise with you, I want you to know that the difficult part is not doing the activity. It is making yourself believe that the activity will have enough benefit that you will put forth the actual effort to do it, and experience the results.

Often when I give this assignment to patients, they come back for two or three weeks afterward, still not having tried it. That's OK; I'm so certain they will not try it initially, that I generally don’t even assign it until I have been working with them for several weeks and have had sufficient time to coach them into understanding the benefits of shifting their and thinking; how it relates to brain functioning; and how it affects their mood, so that they understand the value of what I am asking them to do.

OK, so what is the exercise?

Keep a pad of paper next to your bed and every night before you go to sleep, write down three things you liked about yourself that day.

In the morning, read the list before you get out of bed.

Keep adding three new things to your list every day to keep the list growing.

Do this every day for 30 days.

These don’t have to be big things, like I am a kind person; they can be simple, such as I like that I held the door for my co-worker, or I like that I didn’t lose my temper in traffic today, or I like that I am making the effort to try this exercise even if I’m not sure it will work.

For someone who is depressed, this activity feels like a lot of effort. Why? Research shows that people with have what is referred to as an attentional for negative self-relevant materials. They also have impaired attentional control, which means that once a negative schema is activated, they tend to ruminate on it and have difficulty disengaging and shifting their attention to something else; consequently, there is sustained negative affect. (1) Essentially, people with depression generally spend a good deal of time thinking about what they don’t like about themselves—and they have a hard time stopping.

The more time you spend thinking about something, the more active it becomes in your mental space—and the easier it becomes to access. Also, the more you think of something, the more it primes your brain to keep looking for similar things in your environment, creating a selective filter that not only causes you to sift your environment for things that match up with what you are thinking about, it actually causes you to distort ambiguous information in a way that matches up with your dominant thoughts.

Someone with depression who goes to a party might get 10 compliments, but if one person mentions the shirt he is wearing is “interesting,” that person may likely go home and fixate on the ambiguous comment and turn it into a stream of thinking like this: I wonder what was wrong with my shirt, I probably looked silly in it, I bet they all thought I looked like an idiot. What’s wrong with me? Why can’t I ever get anything right? This is so humiliating. The 10 compliments have long been forgotten.

So how will this exercise help you?

Research also shows that it requires more attentional effort to disengage from a negative thought process than a neutral one. (2) This simple-to-do but nonetheless effortful exercise essentially helps you build the strength to disengage from any negative thought stream; redirects your attention to positive aspects of yourself; and retrains your selective attention bias.

As you do this, you not only start to become aware of more of your positive attributes, they become more available to you as you interpret events around you. Compliments become something you can hear and accept because they are more congruent with your new view of yourself. You start to interpret events occurring around you in a less self-critical way. If you stick with it, over time this has a compounding effect that elevates your overall sense of —and, subsequently, your well-being.

But remember: There is no benefit to your mental health in just understanding how the exercise works, just as there is no benefit to your physical health in knowing how to use a treadmill. The benefit comes from the doing.