Career planning is something which would determine what you want to do with your life, what you end up doing with your life. Career planning is a dynamic process. It definitely needs to be in its rudimentary state while in school and gradually bloom to give a direction by the time one is in college. But career choices can change over time but it generally stays related- one who is not to keen on physics cannot one day wake up at 24years of age and decide to get into research related to physics.