Decide whether to continue from future costs and returns, not what you already spent
Money and time already invested make people more inclined to continue. A review of 98 datasets found this tendency consistently. Count what remains to be invested and what can still be gained; leave irrecoverable past costs out.
What it takes
Free. Accepting that past time is gone and cannot be recovered is the hard part.
What you may gain
Prior money, effort and time increase commitment to continuing—the sunk-cost effect. A meta-analysis of 98 datasets confirmed a reliable effect. Resisting it avoids investing further time merely to feel that earlier time was not wasted.
Context & considerations
For Arkes and Blumer's theater experiment, the source verified only the direction: people paying more attended more performances over six months. Exact group attendance counts remain unverified. Roth and colleagues found the effect weakened over time and was smaller in older people.
Research & references
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