It is narrated from Sayyiduna Abdullah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to supplicate: "O Allah! You have made my creation good, so make my character good as well."
Hadith Referenceالفتح الربانی / كتاب الأذكار والدعوات / 5631
Benefits: … The hadith in which this supplication is specified with a mirror has been narrated by Ibn Sunni, but that narration is weak. Therefore, this supplication is established, but specifying it for any particular occasion is not established. However, it is a separate matter that upon seeing the beauty of one’s own creation, one should recite this supplication.