according to what his condition allows: he may need to refrain from fasting for two-thirds of the time, three-quarters of it, or all of it. Once he has restored his health, he may return to fasting on alternate days if he can do so without harm. Otherwise, he should fast only as much as benefits him and does not distract him from what Allah loves more than fasting. Allah does not love that what is more beloved to Him should be abandoned for something lesser. How, then, could He make that obligatory?

As for the light he experienced through this fasting:

It is well known that acts of worship, as a category, are not wholly evil. Rather, prohibited forms of worship contain both benefit and harm, but because their harm outweighs their benefit, the Lawgiver has forbidden them. Thus, He has forbidden fasting every day, habitually spending the entire night in prayer, and praying after the dawn and afternoon prayers. Yet people experience a light through sustained fasting because of their intense hunger. This is of the same kind as what unbelievers experience, whether among the People of the Book or those without a scripture, such as monks and worshippers of graves. However, this excessive hunger, which goes beyond the prescribed limits, ultimately harms them in this world and the Hereafter, so that the sin it entails outweighs its benefit.

Indeed, we have seen many such people whose excess in the arduous practices they undertake has led them to neglect, discouragement, weariness, and idleness. They may even become entirely cut off from Allah, or be diverted by less meritorious deeds from more meritorious ones, or lose their reason altogether or suffer some impairment of it. This is because their deeds are not founded upon uprightness and adherence to the prophetic example.