Being "filled" means being endowed with a spiritual quality. When the material in question is good -- water, food, people who represent good things, etc. -- it means getting a desire for good and an understanding of truth from the Lord. When the material is bad -- dust, flies, emotions like despair or terror, etc. -- it means being overwhelmed and enslaved by the desire for evil and the false, twisted logic that supports it. There are a number of references in the Bible to "filling the hand," which has a specific meaning and is dealt with separately.

35. Man has two inherent powers of will and understanding. When the understanding is governed by the will they then constitute one mind and so one life; for what a person in that case wills and does he also thinks and intends. But when the understanding is at variance with the will, as it is with people who claim to have faith and yet live otherwise, then a mind previously one is split in two. One half seeks to transport itself into heaven, while the other inclines towards hell. And because the will is what accomplishes everything, the whole man would rush straight into hell unless the Lord took pity on him.