The problem with a single target date
A single date creates a pass/fail outcome from what is genuinely a variable process. Missing a self-imposed date by two weeks can feel like failure, even when the underlying progress was entirely normal.
What research on expectations suggests
Studies on patient expectations in weight-loss treatment have found that overly optimistic timelines are associated with higher rates of premature quitting when reality diverges from the plan -- even when actual progress was clinically meaningful.
How a range changes the planning conversation
Instead of "will I hit my goal by June 1st," a range reframes the question as "what's my realistic window, and where does June 1st fall within it" -- which is both more accurate and less likely to trigger discouragement at the first sign of a normal slowdown.
Applying this to real deadlines
For genuinely fixed external dates (weddings, medical procedures, reunions), working backward from the 90th-percentile end of a realistic range -- rather than the optimistic end -- gives a meaningfully higher chance of being on track when the date arrives.