The first step is to make sure your tree is stable and secure. You may want to consider using a tree skirt or a barrier around the base to prevent the cat from getting close. You can also use deterrents like tin foil, aluminum foil, or double-sided tape on the lower branches to discourage the cat from climbing. Additionally, you can try offering the cat alternative playthings or a scratching post to distract them from the tree. With a little patience and creativity, you can keep your furry friend from ruining your holiday decorations.