Someone once asked Rav Chaim Kniyevsky if there is a mitzva for a chosson to be mesameach ... himself [or the kallah herself]?
He answered that on the pasuk that teaches that there is a mitzva to redeem one's relative who was sold as an עבד there is a מחלוקת in מסכת עבדים [did you learn it recently??:-)] whether this applies to the עבד himself. One opinion states that if it is a mitzva for others to redeem the עבד it is certainly a mitzva for himself to redeem himself. The other opinion differs and claims that it is not.
The same מחלוקת would apply here.
I can see a חילוק but I am sure that Rav Chaim saw the same חילוק....
But apparently it is simple that the chosson and kallah have a mitzva to be mesameach each other. People don't usually think about that...
לזכות החתן והכלה ר' מאיר זאב שטיינמעץ שליט"א ושושנה קמנצקי שתחי' לכבוד שמחת כלולותם מחר בשעה טובה ומוצלחת