When you have a picky cat that doesn't want to eat what you give her or use the litter, praise her after she is the Royal Canin cat food you gave her or she used the litter box, so she knows she has done something good. Find all kinds of rewards in the form of paste or bars; possibly, you can also use a little meat that he used to adore. You don't have to worry if one day your cat refuses food or eats less than usual. Just like humans, there can be days when they have less appetite.