Give tasks a deadline when nobody else has set one
With external deadlines, 80.6% of students finished on time; only 38.7% finished within their own forecast. Completion tracked the deadline much more closely than the estimate. For an open-ended task, set and honor a date.
What it takes
Free. Treat the date as a real commitment; ignoring it defeats the purpose.
What you may gain
In the cited study, 80.6% completed by an external deadline versus 38.7% within their own predicted duration. Actual completion timing strongly correlated with the deadline, r=0.82, but only weakly with their forecasts.
Context & considerations
Telling someone your date can make it closer to an external commitment. The research established effects of externally imposed deadlines, not self-set timeboxes or Pomodoro sessions; extending it to those is an inference.
Research & references
Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the “planning fallacy”: Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366–381. https://doi.org/10.1037/0022-3514.67.3.366