General opposites:
* Dukhi (दुखी) - Sad, unhappy
* Ashanti (अशांत) - Restless, uneasy
* Udas (उदासी) - Depressed, gloomy
* Krodhit (क्रोधित) - Angry
More specific opposites:
* Nirash (निराश) - Disappointed, hopeless
* Chintagrast (चिंताग्रस्त) - Worried, anxious
* Asantu (असंतुष्ट) - Dissatisfied
* Niraash (निराश) - Disheartened, discouraged
The best opposite for "prassanna" will depend on the specific context of the sentence.