de Unamuno, M.
(1954).
Tragic Sense of Life.
"To have recourse to those ambiguous words, 'optimism' and 'pessimism', does not assist us in any way, for frequently they express the very contrary of what those who use them mean to express. To ticket a doctrine with the label of pessimism is not to impugn its validity, and the so-called optimists are not the most efficient in action. I believe, on the contrary, that many of the greatest heroes, perhaps the greatest of all, have been men of despair and that by despair they have accomplished their mighty works." (p. 130)
Hyatt, C., & Gottlieb L.
(1987).
When Smart People Fail.
"There is nothing new about despair. People have experienced it throughout history and literature. Winston Churchill called it his 'black dog'. You feel lonely, sad, depleted, unable to get out of bed in the morning, overwhelmed at the thought of getting dressed, and devoid of hope for the future.
Despair can strike whether or not you have failed, and many people who fail never know its anguish at all. What, then, is the connection? In his book Feelings, psychiatrist Willard Gaylin says:
'Depression occurs when we loase confidence in our own coping mechanisms. We become depressed when we are bankrupt of self-esteem and self-confidence, when we no longer have the sense of our own capacities to insure either our actual survival or the worthiness or value of the life which we can sustain.' " (p. 55)