Sometimes you need to be firm with your Humans. For example, your Human Mommy may tell you that she wants to roll onto her side for her afternoon nap.
Tell her no. Remind her that you are comfortably installed on her chest and that it is her duty, her honor, to continue to stroke your head and muzzle until you you tire of her ministrations.
Under no circumstances is she to alter her position and thereby inconvenience you, the Cat.