So, what do demons so all day?
One thing they do is pick fights with God’s angels over nations and over you.
Another thing they do all day is try to get God to let them touch your body, or to use a sickness or physical disability as a wedge to get into your life and discourage you spiritually.
It may be a simple nuisance, like hay fever. It may be a more serious problem like the flu. It may be a heart problem or even cancer. These fallen angels, through their misguided leader, Satan, argue with God that by touching you, they reveal your lack of faith.
God, however, only allows it when He knows that given enough time, that very sickness or anguish or emotional trauma will work for His glory.