This sound is from Disappointed Soundboard

A person who feels regret focuses on the personal choices that contributed to a poor outcome. Disappointment is the feeling of dissatisfaction that follows the failure of expectations or hopes to manifest. The study of disappointment is a focus in the field of decision analysis, as disappointment is one of two primary emotions involved in decision-making.
See also: Disappointed (disambiguation), The Disappointed, Still Disappointed, Seldom Disappointed, Charles J. Guiteau, and Disappointed (Electronic song).