The perfection of joyful determination is defined as taking delight or feeling joy in doing something positive or virtuous. If you are very joyful about doing negative things or about being busy with meaningless activities, this is not called joyful exertion from a Buddhist point of view. This kind of attitude is actually a form of laziness, an attachment to frivolous activities. Such a person would not be considered diligent at all. But if you are JOYFUL and DETERMINED TO PERFORM POSITIVE ACTIONS, then as a result, you discover and learn many new things that you didn't know about before.