Direct opposites:
* Cheerful: Expressing happiness and optimism.
* Content: Satisfied and at ease.
* Happy: Feeling or showing pleasure or contentment.
* Joyful: Filled with or expressing great joy.
* Optimistic: Hopeful and confident about the future.
Contrasted feelings:
* Indifferent: Not caring or interested.
* Apathetic: Having or showing little or no emotion.
* Detached: Not emotionally involved.
* Dispassionate: Not influenced by emotions or personal feelings.
* Realistic: Concerned with the facts and practicalities of a situation.
More specific contrasts:
* Confident: Feeling sure of oneself and one's abilities.
* Hopeful: Expecting or believing that something good will happen.
* Excited: Feeling a lot of energy and enthusiasm.
* Energetic: Full of energy and enthusiasm.
* Determined: Having a firm intention or purpose.
The best antonym will depend on the specific context in which you're using the word "wistful."