Why do otherwise sincere people keep underestimating how long ordinary tasks will take?

Many late people are not defiant; they are optimistic. Psychologists Daniel Kahneman and Amos Tversky call this the “planning fallacy,” our tendency “to underestimate how long a task will take, even when we’ve performed it many times” (Austin, “Some people are always late”). We picture best‑case scenarios and quietly edit out the interruptions, delays, and complications that almost always appear. That optimism may feel benign, but it reliably produces lateness.

This pattern shows up in ministry, work, and home life. We assume a visit will take thirty minutes, not counting the driveway conversation. We imagine we can answer “just a couple of emails” before leaving, not accounting for the follow‑ups they trigger. The problem is rarely one dramatic miscalculation but a stream of minor underestimates that compound.

Productivity consultant Rashelle Isip recommends a simple, humble countermeasure: deliberately over‑estimate. “If you think something will take 10 minutes,” she advises, “make it 20 to give yourself a buffer” (Austin, “Some people are always late”). That act of doubling our estimate functions as a confession: we admit that we misjudge time and build grace into our schedule. Over time, this habit can convert wishful thinking into realistic planning.

Pastorally, this means we should teach people to see accurate time‑estimation as part of wisdom literature’s call to “walk circumspectly, not as fools, but as wise, redeeming the time” (Ephesians 5:15-16). Naming the planning fallacy helps latecomers move from vague regret to specific, actionable repentance in how they plan their days.

The planning fallacy shows that many late people are optimists about time, and deliberate over‑estimation is a simple act of humility that turns wishful schedules into more faithful ones.

Related Material

• Note-Taking: How to Increase Your Knowledge — applies realistic planning to how you handle knowledge work so ideas actually turn into finished work.
• Living Within Our Limits: Finding Freedom in Less for More — explores limits and margins as gifts, reinforcing the call to build buffers into your schedule.
• Rhythms that Keep You Whole — connects humble time‑estimation with sustainable ministry rhythms that prevent chronic overcommitment.

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Source: On Being a Missionary, by Thomas Hale & Gene Daniels

Disclaimer: Information in my “slip-box” doesn’t necessarily reflect my agreement with the source or all its content. Recording diverse perspectives helps strengthen one’s position beyond the echo chamber of like-minded thinkers. By documenting alternative viewpoints, we engage in the intellectual wrestling match that ultimately deepens our understanding.

I aspire to post one note from my “slip-box” every weekday. If you want to learn more about how to work with knowledge, click this link: What is knowledge management?