* Depressed: This is a general term for feeling low in spirits and lacking energy.
* Dejected: This implies a feeling of discouragement or disappointment.
* Disheartened: This suggests a loss of hope or enthusiasm.
* Downcast: This describes a sad and gloomy demeanor.
* Miserable: This refers to extreme unhappiness.
* Gloomy: This implies a pessimistic outlook.
* Despondent: This is a strong word for feeling hopeless and discouraged.
The best opposite will depend on the specific nuance you want to convey.