Setting certain goals for yourself will give you a sense of purpose, if you need one. This is not meant to be too serious in the beginning, just a way to help you better determine your destinations from the endless number of places to see and things to do. Your goal may be to experience the most fascinating and unusual places in the world, or just see those romantic places you thought you would never get to. Trying to do too much can exhaust you and end up defeating the purpose of the trip. Going slower will lend itself to different experiences, such as meeting more people and learning more about the cultures.
People travel for many different reasons, with many different interests, in many different ways.
It is quite important in the planning, especially if you are travelling with a companion, to get some things established up front. For most this is quite simply to satisfy curiosity, see things while you have the means and energy, take the opportunity to broaden your knowledge of people, places, cultures etc. It is good to have similar goals to that of your companion, or at least an understanding.