When deciding whether to continue, consider only future investments and future returns — not what has already been invested.

No monetary cost is involved. The difficulty lies in accepting that all time previously invested cannot be recovered.

Prior investments of money, effort, and time increase the likelihood of continued engagement. This phenomenon is known in psychology as the sunk cost effect. Across 98 datasets, this effect has been confirmed as stable. Avoiding this bias saves valuable future time that would otherwise be wasted due to a desire not to “waste” past efforts.

Arkes, H. R., & Blumer, C. (1985). The psychology of sunk cost. Organizational Behavior and Human Decision Processes, 35, 124–140. https://doi.org/10.1016/0749-5978(85)90049-4；Roth, S., Robbert, T., & Straus, L. (2015). On the sunk-cost effect in economic decision-making: A meta-analytic review. Business Research, 8(1), 99–138. https://doi.org/10.1007/s40685-014-0014-8

That theater experiment by Arkes and Blumer was conducted this way. The University of Ohio theater sold season tickets, randomly assigning purchasers to one of three prices: the original price of 15 USD, a discount of 2 USD, or a discount of 7 USD. During the first half of the season, the group at the original price watched an average of 4.11 shows, while the other two groups watched 3.32 and 3.29 shows, respectively. In the second half of the season, there was no significant difference among the three groups. Roth et al. found that this effect fades over time, and older individuals are less affected.