The fanatical man never has peace of mind and who has been alienated from peace, has been alienated from joy.
It is called peace of mind and is actually the perfect (mental) health, while fanaticism is opposed to peace. So the one who has fanaticism is seriously ill.
Fanaticism is not a trait of wisdom, but a disease of the soul, because it reveals a narrow and limited perception, due to a lot of ignorance. So the one who has fanaticism is seriously ill.
Saint Isaac the Syrian