a sudden change from something exciting or important to something much less exciting or important (causing disappointment)

ineffective conclusion

the sudden change from something interesting, noble etc to something ridiculous or insincere (often deliberately for humorous effect)

sentimentality

the feeling of strong fear and discouragement

disappointed feeling; distress

to be sad, depressed

depression

unhappiness, depression

unhappiness, depression

a serious fall (in prices etc); a period when business is bad; (of a person) to sit down, fall, heavily

decline, failure