Without stimulus or focus, the individual is confronted with nothingness, the meaninglessness of existence, and experiences existential anxiety. Heidegger states this idea as follows: "Profound boredom, drifting here and there in the abysses of our existence like a muffling fog, removes all things and men and oneself along with it into a remarkable indifference. This boredom reveals being as a whole."[27] Schopenhauer used the existence of boredom in an attempt to prove the vanity of human existence, stating, "...for if life, in the desire for which our essence and existence consists, possessed in itself a positive value and real content, there would be no such thing as boredom: mere existence would fulfil and satisfy us."[28]
Flow is a state of total immersion in a task that is challenging yet closely matched to one’s abilities, akin to “being in the zone.” Flow occurs when a person’s skills match the level of challenge presented by the environment and when a task includes clear goals and immediate feedback. Tasks that are too easy are boring. In contrast, tasks that people perceive to be too difficult lead to anxiety.

This kind of boredom is different from the others. Like reactant boredom, it’s also unpleasant, but a person experiencing it has low arousal and a lack of positive or negative feelings–in other words, a feeling of helplessness or depression. Of the high school students sampled in the study, 36% of boredom experiences were of the apathetic kind, which is worrisome given that other studies have shown that boredom, depression, and destructive behaviors are often linked.

The highest levels of arousal and negative emotions. A person in a reactant boredom state has a strong motivation to escape his or her boring situation and avoid those responsible for it (such as teachers or a boss). Reflects significant restlessness and aggression. There are persistent thoughts about specific, “more highly valued alternative situations.”
Absent-mindedness is where a person shows inattentive or forgetful behaviour.[20] Absent-mindedness is a mental condition in which the subject experiences low levels of attention and frequent distraction. Absent-mindedness is not a diagnosed condition but rather a symptom of boredom and sleepiness which people experience in their daily lives. When suffering from absent-mindedness, people tend to show signs of memory lapse and weak recollection of recently occurring events. This can usually be a result of a variety of other conditions often diagnosed by clinicians such as attention deficit hyperactivity disorder and depression. In addition to absent-mindedness leading to an array of consequences affecting daily life, it can have as more severe, long-term problems.
Boredom also has its benefits. It is important to see boredom as a “call to action” (Svendsen, 1999). Nietzsche suggested that men of rare sensibility value boredom as an impetus to achievement. Boredom can be a catalyst for action. It can provide an opportunity for thought and reflection. It can also be a sign that a task is a waste of time—and thus not worth continuing.
In conventional usage, boredom is an emotional and occasionally psychological state experienced when an individual is left without anything in particular to do, is not interested in their surroundings, or feels that a day or period is dull or tedious. It is also understood by scholars as a modern phenomenon which has a cultural dimension. "There is no universally accepted definition of boredom. But whatever it is, researchers argue, it is not simply another name for depression or apathy. It seems to be a specific mental state that people find unpleasant—a lack of stimulation that leaves them craving relief, with a host of behavioural, medical and social consequences."[1] According to BBC News, boredom "...can be a dangerous and disruptive state of mind that damages your health"; yet research "...suggest[s] that without boredom we couldn't achieve our creative feats."[2]
The bored antihero became prominent in early 20th century existentialist works such as Franz Kafka's The Metamorphosis (1915),[43] Jean-Paul Sartre's La Nausée (1938) (French for 'Nausea'),[44] and Albert Camus' L'Étranger (1942) (French for 'The Stranger').[45] The protagonist in these works is an indecisive central character who drifts through his life and is marked by ennui, angst, and alienation.[46]
What can you do about boredom? Obviously, there are times when you are stuck. If you are listening to a lecture that you cannot leave, then you just need to find a way to get through it. When you have some control, though, use your understanding of boredom to help you out. If you can, try to do a meditation exercise to lower your arousal level. Also, keep some music handy. Music you enjoy can crowd out distractions in the environment. It can also influence your mood in positive ways to counteract the pain of being bored.  
The most common way to define boredom in Western culture is having nothing to do. Boredom is generally viewed as an unpleasant emotional state in which the individual feels a pervasive lack of interest in and difficulty concentrating on the current activity. The condition corresponds more precisely to the French ennui, an existential perception of life’s futility. Ennui is a consequence of unfulfilled aspirations (Goodstein, 2005).