#31: How to Use the Sunk Cost Fallacy to Make Habits Stick

I love soft drinks so much I used to drink glasses of them almost every day (especially on hot days).

But I also know how unhealthy it is, so I decided to try to skip soft drinks. I'm on my third week without a sip of ice-cold Coke now. No small feat, considering how I consider most meals incomplete without that sweet, fizzy drink.

So how did this even happen?

I have a fitness accountability group where we pledge whatever kind of movement we want to do each day or how much time we'll spend on exercise. Each day, we update the group with a simple message like this: Day 1: One hour of Pilates and a 10 minute walk with my dog.

I added a "Skip soft drinks" pledge and sent updates every day. Today, I write, Day 21 of skipping soft drinks.

The twist? You skip a day, and you're back to Day 1—even if you were already on Day 54.

My accountability group and desire to be healthier got me this far in this simple no-soft drinks challenge. But another thing helped: the sunk cost fallacy.

Oxford Languages defines sunk-cost fallacy as "the phenomenon whereby a person is reluctant to abandon a strategy or course of action because they have invested heavily in it, even when it is clear that abandonment would be more beneficial."

The Decision Lab briefly explains how this bias came to be:

"Behavioral scientists and economists are constantly trying to understand the reasons why we make irrational decisions. Richard Thaler, a pioneer of behavioral science, first introduced the sunk cost fallacy, suggesting that “paying for the right to use a good or service will increase the rate at which the good will be utilized” (1980, pp. 47).7

Two important psychologists, Hal Arkes and Catherine Blumer, wanted to examine the sunk cost effect in practice to expand Thaler’s definition beyond money. They defined the fallacy as “a greater tendency to continue an endeavor once an investment in money, effort, or time has been made” (1985, pp. 124).8"

On days I felt most tempted to give up and drink a glass of soda, I always thought about the progress I've made, the effort and time I've put into not drinking soda.

And while the sunk-cost fallacy is often referenced when explaining irrational buying decisions, we can actually use it to make our habits stick.

Want to write for 30 days? Invest in a cohort-based course like Ship 30 for 30.*

Want to learn how to play a guitar? Buy one and hire someone to teach you.

Want to be motivated about a project? Keep a log of all the time and resources you've put in to it and remind yourself how much you've invested in it—financially and emotionally.

P.S. Items marked with * are affiliate links. When you purchase products through those links, I may get a commission at NO EXTRA COST to you. Pinkie promise, I’ll only recommend stuff I actually use and love! 💖

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Hi, and thanks for reading! I'm Kishly, a cheerleader of creatives and copywriter turned marketing strategist. Bookmark this blog to read my daily atomic essays on marketing, compassionate productivity, creative living, and lifelong learning. Or subscribe to Process, my weekly-ish newsletter for young adults (and the young at heart) in pursuit of wisdom and wonder. ✨

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