Presumptively goal x is chosen with goal z in mind, goal z being that person's inculcated beliefs about what's generally most valuable in life. Now, how was goal z chosen? From life experiences, from friends and family, from other goals. And where did those other goals come from? Still other goals/priorities, and it's turtles all the way down. Possibly, if you really dig into it, goal z winds up justifying goal z to some extent. But even if you take the time to precisely order your whole philosophy of life so that everything from the person you marry to the shoes you wear ultimately fits into one single end goal...how is that end goal "rationally" chosen?