I'm really sorry to hear that mate, it's amazing how strong a bond you can build with a pet, working as a dog walker and pet sitter I've had to say goodbye too many times in the last few years, the way i approach it (after floods of tears) is to focus on having that bond and being thankful you were able to share your time with them, it's better to have had that bond for a short time than not at all, cats are awesome.