How can one emulate the Prophet Muhammad (peace be upon him) in his supererogatory fasting and prayers, and what is the meaning of Aisha's (may Allah be pleased with her) saying: "And who can do what the Messenger of Allah did, for all his deeds were continuous"?

The Messenger, peace and blessings be upon him, is the excellent role model in every deed, and emulating him in his Sunnah is not merely a legal emulation. Acts of worship are of two types: obligatory duties (fara'id) which must be performed in a manner that is sufficient and most complete, and supererogatory acts (nawafil) which are difficult for a Muslim to consistently maintain as the Messenger did, but he is required to perform them to the best of his ability. The actions of the Messenger, peace and blessings be upon him, were always continuous and not confined to specific days.