Literal translations:
* Tu as trouvé ton bonheur. (This is the most direct and common translation.)
* Vous avez trouvé votre bonheur. (This is the formal version, used when addressing someone with respect.)
More poetic translations:
* Tu as trouvé ton chemin vers le bonheur. (You have found your path to happiness.)
* Tu as trouvé ton épanouissement. (You have found your fulfillment.)
* Le bonheur t'a trouvé. (Happiness has found you.)
The best translation will depend on the context and the desired effect.