Loss of Magical Abilities

 

Are there any natural circumstances in which a magic user can lose their magical abilities?
>Can magical abilities be lost as a person ages?
>Can magical abilities be lost as a result of an injury or illness?

Are there any unnatural circumstances in which a magic user can lose their abilities?
>Are there types of spells or curses that can render the target unable to use magic?
>>Are there any permanent ones?

Can magic ability be lost as a result of magical burnout?
>How much magic does an average caster have to use before they experience burnout?
>>Does it gradually build until the caster cannot take it anymore, or does it like a sudden shut-off of magical abilities?
>How long are the magical abilities gone for when this happens?
>Can this cause permanent loss of magical abilities?
>Are there types of magic that do not contribute toward magical burnout?
>What is required to regain use of magical abilities?
>>Sleep?
>>Meditation?
>>Drinking a potion?
>>Waiting until it ends?