Is it permissible to repeat Surat Al-Fatihah or any other recitation in the prayer within the same rak'ah if the worshiper makes a mistake while reciting it?

If someone doubts whether they recited Al-Fatihah completely after finishing it, or if they were thinking about something else while reciting it, they are not required to repeat it. This is because doubt after completing an action does not affect it. However, if they doubt before completing it, or doubt whether they recited it at all, then they must resume the recitation.