Pratyahara means alternative food. It means to refrain or refuse from eating food you usally have and choosing something else to eat . Our sense have tendency to go outwards. To bring them inwards we need a different regime of food and set of thoughts. That is pratyahara. Just as we give a pacifier to crying babies to calm them, similarly we give alternatives to a mind that is resrless and not a peace. That is pratyahara. Going inward in first step.