Obviously, it's evolutionarily advantageous for us to remind ourselves of tasks we have yet to finish, and experimentally it has long been observed that unmet goals keep popping into people's minds.
This is know as the Zeigarnik effect.
For example, when students are asked to think about upcoming exams and then asked to complete partial words such as "re_" or "ex_", they complete them as "read" or "exam" instead of "real" or "exit", more often than students who were first asked to think about upcoming parties instead of exams.
And when people were asked to think of uncompleted projects, and then instructed to read part of a novel, their minds tended to wander.
Now here's the interesting and almost unbelievable part: if subjects were asked to formulate study plans for their upcoming exams and to write down plans to complete their unfinished tasks, the Zeigarnik effect disappeared.
So to find inner peace, free from self-nagging, make a plan.
- Willpower, 2011 book by Roy Baumeister & John Tierney, pages 80-4
- "Consider it Done!: Making a Plan Eliminates the Zeigarnik Effect", E.J. Masicampo & R.F. Baumeister, manuscript submitted for publication, Tufts Univesity