…not only do they hold you accountable for what you will do, but they also help you be reasonable about what you will do!
For instance, you might say “I commit to going through all the files today in the closet until I am finished.”

Your Accountability Partner may challenge you (a coaching skill) to commit to 15 minutes. And then if you want to keep going, do another 15. And if you want to keep going, another 15.
In this way you will achieve your goal….and feel good about yourself!