The magic in that country was so thick and tenacious that it settled over the land like chalk-dust and over floors and shelves like slightly sticky plaster-dust. (Housecleaners in that country earned unusually good wages.) If you lived in that country, you had to de-scale your kettle of its encrustation of magic at least once a week, because if you didn't, you might find yourself pouring hissing snakes or pond slime into your teapot instead of water.
Robin McKinleyWhat you describe is how it happens to everyone: magic does slide through you, and disappear, and come back later looking like something else. And I'm sorry to tell you this, but where your magic lives will always be a great dark space with scraps you fumble for. You must learn to sniff them out in the dark.
Robin McKinley