Present bias.
A cost today can crowd out a benefit you know you want later.
The version of you making a plan is not always the version that has to follow it. The gap is clearest when acting now takes effort.
$17 a visit
What gym members paying a flat fee over $70 a month actually spent per visit, with a $10-a-visit pass on offer. On average they gave up about $600.
Decide now, out loud, on a specific plan, and put something on the line so backing out costs you. The strong results all come from studies with money at stake, so a soft pledge is a weaker thing than the study measures.
This one holds up.
Also under Preferences.
DellaVigna & Malmendier 2006 · Augenblick, Niederle & Sprenger 2015 · Royer, Stehr & Sydnor 2015 · Laibson 1997 · O'Donoghue & Rabin 1999