" Many systems require slack in order to work well. Old reel-to-reel tape recorders needed an extra bit of tape fed into the mechanism to ensure that the tape wouldn't rip. Your coffee grinder won't grind if you overstuff it. Roadways operate best below 70 percent capacity; traffic jams are caused by lack of slack. "

― Sendhil Mullainathan , Scarcity: Why Having Too Little Means So Much