Procrastination is the practice of carrying out less urgent tasks in preference to more urgent ones, or doing more pleasurable things in place of less pleasurable ones, and thus putting off impending tasks to a later time. According to Freud, the pleasure principle may be responsible for procrastination; humans prefer to avoid negative emotions, and to delay stressful tasks. The belief that humans work best under pressure provides an additional incentive to postponement of tasks. Some psychologists cite such behavior as a mechanism for coping with the anxiety associated with starting or completing any task or decision. Other psychologists indicate that anxiety is just as likely to get people to start working early as late and the focus should be impulsiveness. That is, anxiety will cause people to delay only if they are impulsive. Schraw, Wadkins, and Olafson have proposed three criteria for a behavior to be classified as procrastination: it must be counterproductive, needless, and delaying. Similarly, Steel (2007) reviews all previous attempts to define procrastination, indicating it is "to voluntarily delay an intended course of action despite expecting to be worse off for the delay." Procrastination may result in stress, a sense of guilt and crisis, severe loss of personal productivity, as well as social disapproval for not meeting responsibilities or commitments. These feelings combined may promote further procrastination. While it is regarded as normal for people to procrastinate to some degree, it becomes a problem when it impedes normal functioning. Chronic procrastination may be a sign of an underlying psychological disorder. Such procrastinators may have difficulty seeking support due to social stigma and the belief that task-aversion is caused by laziness, low willpower or low ambition.  On the other hand many regard procrastination as a useful way of identifying what is important to us personally as it is rare to procrastinate when one truly values the task at hand.