Denial involves blocking external events from awareness. For example, if a particular situation is too much for a person to handle, he or she simply refuses to allow the experience to become reality for them, despite the fact that it happened. The use of denial is a primitive and dangerous defense because eventually the individual must face reality. The longer one attempts to deny the objective reality, the greater may be the consequences. Denial can operate by itself or, more commonly, in combination with other, more subtle defense mechanisms that support it.
Denial can be unconscious as when a dying person refuses to admit that their life will soon end or when a person with a heart condition denies that their overeating or smoking is of any consequence. It can also take a semi-conscious state where the individual accepts a portion of the situation but denies another. For instance, a person may acknowledge that they were in an automobile accident but they will not accept the fact that a loved one who was critically injured might die.