The sunk-cost fallacy teaches that we tend to overvalue things we’ve already invested time or money in. Tim Ferriss recommends using the sunk-cost fallacy (in our favor) as a tool to improve our odds of follow- through. By paying for things in advance—like a gym membership, restorative vacation, or learning seminar—we’ll be more likely to take (and continue) the desired action. I love this hack because it flips the script on behavioral psychology that usually works against us into one that works for us.
Source: Ben Meer