Formal:
* With dignity
* With honor
* With self-respect
* With a sense of accomplishment
* With a sense of achievement
* With a sense of satisfaction
* With a sense of pride
* With a feeling of triumph
Informal:
* Bravely
* Boldly
* With confidence
* With assurance
* With swagger
* With a flourish
* With a strut
* With a beaming smile
Other options:
* Arrogantly (can have a negative connotation)
* Boastfully (can have a negative connotation)
* Triumphantly
* Victoriously
* Magnificently
* Grandly
The best word to use will depend on the specific situation and the tone you want to convey.