Achievement: Players have multiple paths to achieve progress, completion, and power. When one is close to a milestone, it is easy to justify playing for a few more minutes to reach the next step before quitting. It is easiest to stop playing when a goal has been reached. But as soon as you reach a point, another point in character, trophy, reward, or achievement is close to finishing, so they decide to play until it does too. It's a potentially endless cycle.